Celestron 31056, 31058 User Manual

C150-HD AND G-8N NEWTONIAN

INSTRUCTION MANUAL

Models #31056 and #31058

TABLE OF CONTENTS

▲▲

▲ INTRODUCTION .................................................................................................................................................. 5

▲▲

How to Use This Manual ................................................................................................................................ 6

A Word of Caution.......................................................................................................................................... 6

The Newtonian Optical System ...................................................................................................................... 7

▲▲

▲ ASSEMBLING YOUR NEWTONIAN ................................................................................................................. 8

▲▲

Unpacking Your Telescope ............................................................................................................................ 8

Setting Up the Tripod ................................................................................................................................... 11

Adjusting the Tripod Height ........................................................................................................................ 11

Attaching the Accessory Tray....................................................................................................................... 12

Attaching the Equatorial Mount .................................................................................................................. 13

Attaching the R.A. Slow Motion Knob .......................................................................................... 14

Attaching the Declination Slow Motion Knob .............................................................................. 15

Installing the Counterweight Bar & Counterweights .................................................................... 16

Attaching the Telescope to the Mount ......................................................................................................... 17

Balancing the Telescope in R.A..................................................................................................... 19

Balancing the Telescope in DEC ................................................................................................... 20

Adjusting the Mount in Altitude .................................................................................................................. 21

Adjusting the Mount in Azimuth ................................................................................................................. 21

Disassembling and Transporting Your G-8N................................................................................................ 22

Storing Your Telescope ................................................................................................................................ 22

Installing the Finderscope ............................................................................................................................ 23

Installing the Eyepiece ................................................................................................................................. 24

Technical Specifications .............................................................................................................................. 25

▲▲

▲ TELESCOPE BASICS ........................................................................................................................................ 26

▲▲

Image Orientation ......................................................................................................................................... 26

Focusing........................................................................................................................................................ 27

Aligning the Finder....................................................................................................................................... 28

Your First Look ............................................................................................................................................. 29

Daytime Observing......................................................................................................................... 29

Nighttime Observing ...................................................................................................................... 30

Calculating Magnification (Power) .............................................................................................................. 31

Determining the Field of View ..................................................................................................................... 31

▲▲

▲ ASTRONOMY BASICS ....................................................................................................................................... 32

▲▲

The Celestial Coordinate System ................................................................................................................. 32

Motion of the Stars ....................................................................................................................................... 33

Polar Alignment ............................................................................................................................................ 34

Finding the Pole............................................................................................................................................ 35

Latitude Scales .............................................................................................................................................. 36

Pointing at Polaris......................................................................................................................................... 37

Declination Drift ........................................................................................................................................... 38

Polar Axis Finder .......................................................................................................................................... 39

Aligning the R.A. Setting Circle .................................................................................................................. 39

▲ ▲

▲ CELESTIAL OBSERVING ................................................................................................................................ 40

▲ ▲

Table of Contents • i

Observing the Moon ..................................................................................................................................... 40

Observing the Planets ................................................................................................................................... 40

Observing the Sun......................................................................................................................................... 41

Observing Deep-Sky Objects ........................................................................................................................ 41

Using the Setting Circles................................................................................................................ 42

Star Hopping................................................................................................................................... 43

Viewing Conditions ...................................................................................................................................... 45

Transparency .................................................................................................................................. 45

Sky Illumination ............................................................................................................................. 45

Seeing ............................................................................................................................................. 45

▲ ▲

▲ CELESTIAL PHOTOGRAPHY ........................................................................................................................ 47

▲ ▲

Short Exposure Prime Focus ......................................................................................................................... 48

Piggyback ..................................................................................................................................................... 49

▲▲

▲ TELESCOPE MAINTENANCE......................................................................................................................... 51

▲▲

Care and Cleaning of the Optics................................................................................................................... 51

Collimation ................................................................................................................................................... 51

▲▲

▲ OPTIONAL ACCESSORIES .............................................................................................................................. 53

▲▲

▲▲

▲ THE MESSIER CATALOG................................................................................................................................ 56

▲▲

▲▲

▲ LIST OF BRIGHT STARS.................................................................................................................................. 59

▲▲

▲▲

▲ FOR FURTHER READING ................................................................................................................................ 60

▲▲

ii • Table of Contents

INTRODUCTION

Welcome to the Celestron world of amateur astronomy! Celestron has been

providing amateur astronomers with the tools to explore the universe for more

than a quarter of a century. The Celestron Newtonian telescope continues in this

proud tradition. With a mirror diameter of 6", your C150-HD has almost 500 times

the light gathering power of the unaided human eye. The G-8N, with its 8" diameter

mirror gathers almost 800 times the light of your eye. It can show you literally

thousands of deep-sky objects. Yet your Celestron Newtonian telescope is compact

enough to take to the mountains or desert or wherever you observe.

This telescope is made of the highest quality materials to ensure durability and

stability. All this adds up to a telescope that gives you a lifetime of pleasure with a

minimal amount of maintenance. And, your Celestron telescope is versatile. It

grows as your interest grows. All you need to do is take the time to familiarize

yourself with your telescope and its operation.

Introduction • 5

How to Use this Manual

This manual is designed to instruct you in the proper use of your Celestron
Newtonian telescope. The instructions are for assembly, initial use, long term
operation, and maintenance. There are seven major sections to the manual. The first
section covers the proper procedure for setting up your Celestron telescope. This
includes setting up the tripod, attaching the telescope to the mount, balancing the
telescope, etc.

The second section deals with the basics of telescope use. Topics include focusing,
aligning the finder, and taking your first look. The third section deals with the
basics of astronomy which includes the celestial coordinate system, the motions of
the stars, and polar alignment. The fourth section deals with celestial observing
covering visual observations of the planets and deep-sky objects. Using both the
setting circles and star hopping are discussed. The fifth section covers celestial
photography working from the easiest to the most difficult. The last major section
is on telescope maintenance, specifically on cleaning and collimation. Keeping

your telescope in proper collimation is the single most important thing you can
do to ensure it performs well.

In addition to the major sections mentioned previously, there is a list of optional
accessories for your telescope that include a brief description of its purpose. This is
the section to consult when you’ve mastered the basics and ready for new, more
challenging observations. The final part of this manual contains a list of objects
that can be observed through your Celestron telescope. Included are the coordinates
for each object, its brightness, and a code which indicates what type of an object it
is. In addition, there is a list of bright stars used for aligning the setting circles.

A Word of Caution!

WARNING ! NEVER LOOK DIRECTLY AT THE SUN WITH THE NAKED EYE

Read the assembly instructions through completely before you attempt to set up
your telescope. Then, once you’ve set up your telescope, read the section on
“Telescope Basics” before you take it outside and use it. This will ensure that you
are familiar with your telescope before you try to use it under a dark sky. Since it
will take a few observing sessions to familiarize yourself with your telescope, you
should keep this manual handy until you have fully mastered your telescope’s
operation. After that, save the manual for future reference.

Your Celestron telescope is designed to give you hours of fun and rewarding
observations. However, there are a few things to consider before using your tele­scope that will ensure your safety and protect your eyes and your equipment.

OR WITH A TELESCOPE. NEVER POINT YOUR TELESCOPE AT
THE SUN UNLESS YOU HAVE THE PROPER SOLAR FILTER.
PERMANENT AND IRREVERSIBLE EYE DAMAGE MAY RE­SULT AS WELL AS DAMAGE TO YOUR TELESCOPE.

NEVER USE YOUR TELESCOPE TO PROJECT AN IMAGE OF
THE SUN ONTO ANY SURFACE. INTERNAL HEAT BUILD-UP
CAN DAMAGE ANY ACCESSORIES ATTACHED TO THE TELE­SCOPE.

NEVER LEAVE THE TELESCOPE UNSUPERVISED, ESPECIALLY WHEN
CHILDREN ARE PRESENT OR OTHER ADULTS WHO MAY NOT BE

6 • Introduction

FAMILIAR WITH THE CORRECT OPERATING PROCEDURES OF YOUR
TELESCOPE.

NEVER USE AN EYEPIECE SOLAR FILTER OR A HERSCHEL
WEDGE SOLAR FILTER. INTERNAL HEAT BUILD-UP INSIDE
THE TELESCOPE CAN CAUSE THESE DEVICES TO CRACK OR
BREAK.

NEVER POINT YOUR TELESCOPE AT THE SUN UNLESS USING
THE PROPER SOLAR FILTER. WHEN USING A SOLAR FILTER,
ALWAYS COVER THE FINDER. ALTHOUGH SMALL IN APER­TURE, THE FINDER HAS ENOUGH LIGHT GATHERING
POWER TO POSSIBLY CAUSE PERMANENT AND IRREVERS­IBLE EYE DAMAGE. THE IMAGE PROJECTED BY THE
FINDER IS HOT ENOUGH TO BURN SKIN OR CLOTHING.

The Newtonian
Optical System

The Newtonian reflector was developed by Isaac Newton in the late 1600’s and
therefore carries his name. This type of telescope uses a primary mirror to focus
the light rays it collects. In addition to focusing the light, the mirror also redirects
them toward the front of the telescope tube where the light entered. Near the front
of the tube, the light rays are intercepted by a small flat secondary mirror (some­times called an elliptical flat) and directed out of the telescope tube at a 90° angle to
the incoming light rays (see figure 1-1). It is here that the eyepiece is placed to
view the image formed by the telescope. Because mirrors, not lenses, are used,
much larger light gathering areas can be used without fear of gravity distorting
them. Furthermore, these larger aperture systems become much more portable
that comparable refractors.

Figure 1-1

This cross sectional diagram shows the light path of the Newtonian optical system. All
optical elements are labeled.

Introduction • 7

ASSEMBLING YOUR N E W T O N I A N T E L E S C O P E

This section covers the proper assembly instructions for your G-8N and C150-HD
reflecting telescope. These telescopes are Newtonian reflector that utilize mirrors
with specific focal lengths. The telescope comes on the German equatorial
mount, which when properly aligned and fitted with the optional motors, will track
objects as they move across the sky. Each telescope contains the following standard
accessories. Included are:

• 20mm Eyepiece 1-1/4"

• 6x30mm Finder (Model #31056)

• 9x50mm Finder (Model #31058)

• Quick Release Finder Bracket

• Lens Cap

• CG-4 German Equatorial Mount (Model #31056)

• CG-5 German Equatorial Mount (Model #31058)

• Counterweight Bar

• Counterweight (5 kg for Model #31058 - 3.6kg and 1.8kg for Model #31056)

• Declination (DEC) Slow Motion Knob

• Right Ascension (R.A.) Slow Motion Knob

• Adjustable Aluminium Tripod

• Accessory Tray

Unpacking Your
G-8N

When setting up the telescope, find a large, clear area where the parts can be laid out
without fear of losing them. Start with the tripod and mount. Remove the contents
of the box and place them neatly on your work surface. Leave the optical tube in its
box until you are ready to attach it to the mount. Once your telescope has been
unpacked and assembled, you will not need the shipping boxes for everyday storage
and transportation. However, you should save them in case you decide to ship your
telescope via a common carrier.

8 • The C150-HD

15
14

13

12

The G-8N

1

2

3
4

5

6

7

10

9

Figure 2-1

G-8N with CG-5 Equatorial Mount

1. Finderscope 9. Tripod Leg Clamp

2. Finderscope Bracket 10. Leg Brace Assembly

3. Tube Ring 11. Counterweight

4. Piggyback Adapter 12. Counterweight Shaft

5. Latitude Scale 13. Equatorial Mount

6. Latitude Adjustment Screw 14. Focuser

7. Tripod 15. Eyepiece

8. Accessory Tray

8

The G-8N • 9

15
14

The C150-HD

1
2

3

13

12

11

10

4

5

6
7

8

9

1. FinderscopeBracket 9. Accessory Tray

2. Finderscope 10. Counterweight

3. Tube Ring 11. Counterweight Shaft

4. Primary Mirror (inside tube) 12. Declination Circle

5. Solw Motion Cables 13. Mounting Platform

6. Latitude Scale 14. Eyepiece

7. Latitude Adjustment Screw 15. Secondary Mirror

8. Tripod

10 • The C150-HD

Figure 2-1A

C150-HD with CG-4 Equatorial Mount

Assembling the Equatorial Mount

Setting Up the Tripod

Adjusting the Tripod
Height

The tripod comes fully assembled with the metal plate, called the tripod head, that
holds the legs together at the top. In addition, the brackets that support the acces­sory tray are also attached to the tripod.

Stand the tripod upright and pull the tripod legs apart until the leg brace assembly
for the accessory tray is fully extended (see figure 2-2). The tripod will now stand
by itself. To increase the stability, tighten the bolts that hold the legs to the tripod
head (use the appropriate size wrench from the supplied set). This will help mini­mize any flexure or wobble of the legs.

Once the tripod is set up, you can adjust the height at which it stands. To do
this:

1. Loosen the knob on the leg clamp so that the tripod leg can be adjusted.

2. Slide the center portion of the tripod leg away from the tripod head until it
is at the desired height.

3. Tighten the knobs on each leg clamp to hold the legs in place.

With the tripod set up, you are ready to attach the accessory tray to the tripod.

Figure 2-2

Setting up the tripod requires nothing more than pulling the tripod legs away from the
tripod head. The height at which the tripod stands can be adjusted by sliding the slats
in the center of each leg toward or away from the tripod head.

The G-8N • 11

Attaching the Accessory
Tray

There are three wing bolts that hold the accessory tray to the center leg brace.

1. Locate the three wing bolts.

2. Place the accessory tray over the leg brace and position it so the thread holes in
the accessory tray are above the slotted holes in the bracket.

3. Insert the wing bolts up through the slotted holes in the leg brace (see figure 2-

3).

4. Thread the wing bolts into the holes in the accessory tray.

5. Tighten the wing bolts fully.

With the accessory tray in place, the tripod will be much more stable making it
easier to attach the mount and telescope.

12 • The C150-HD

Figure 2-3

Attaching the Equatorial
Mount

The equatorial mount allows you to tilt the telescope’s axis of rotation so that you
can track the stars as they move across the sky. The CG-4 and CG-5 mounts are
German equatorial mounts that attache to the tripod head (i.e., metal plate on the
tripod). On one side of the plate there is an “N” which signifies north. This side of
the tripod will face north when setting up for an astronomical observing session.
Above the “N” is a peg about 3/4" high that points straight up. To attach the
equatorial head:

1. Locate the azimuth adjustment screws on the equatorial mount.

2. Retract the screws so they no longer extend into the azimuth housing

(rectangular extrusion) on the mount. Do NOT remove the screws since

they are needed later for polar alignment.

3. Hold the equatorial mount over the tripod head so that the azimuth housing

is above the metal peg.

4. Place the equatorial mount on the tripod head so that the two are flush.

5. Tighten the knob on the underside of the tripod head to hold the equatorial

mount firmly in place. The knob is already attached and can NOT be
removed.

Figure 2-4

The G-8N • 13

Attaching the R.A. Slow Motion Knob

With the mount securely in place, you are ready to attach some of the accessories
(the telescope tube will be added last). Start with the Right Ascension (R.A.) slow
motion knob. The R.A. slow motion knob allows you to make fine pointing
adjustments in the direction the telescope is aiming (once it is attached to the
mount). To install the knob:

1. Locate the hard plastic shell under the R.A. shafts.

2. Remove either of the two oval tabs by pulling tightly.

3. Line up the flat area on the inner portion of the R.A. slow motion knob with
the flat area on the R.A. shaft..

4. Slide the R.A. slow motion knob onto the R.A. shaft.

The knob is a tension fit, so sliding it on holds it in place. As mentioned
above, there are two R.A. shafts, one on either side of the mount. It makes no
difference which shaft you use since both work the same. Use whichever one
you find more convenient. If, after a few observing sessions, you find the R.A.
slow motion knob is more accessible from the other side, pull firmly to remove
the knob, then install it on the opposite side.

Mounting Platform

Mounting Platform

Safety Screw

DEC Slow Motion

Knob

R.A. Setting

Circle

Polar Housing

Cover

Altitude Adjustment

Control

Telescope
Mounting Screw

DEC Lock
Lever

RA Lock
Lever

Declination Setting
Circle

R.A. Slow Motion
Knob

Azimuth Adjustment
Controls

Figure 2-5

The CG-5 Equatorial Mount

14 • The C150-HD

Attaching the Declination Slow Motion Knob

Like the R.A. slow motion knob, the DEC slow motion knob allows you to
make fine pointing adjustments in the direction the telescope is pointed.

The DEC slow motion knob attaches in the same manner as the R.A. knob. The shaft
that the DEC slow motion knob fits over is toward the top of the mount, just below
the telescope mounting platform. Once again, you have two shafts to choose from.
Use the shaft that is pointing toward the ground. This makes it easy to reach while
looking through the telescope, something which is quite important when you are
observing.

1. Line up the flat area on the inner portion of the DEC slow motion knob with

the flat area on the DEC shaft.

2. Slide the DEC slow motion knob over the DEC shaft (see figure 2-6).

Figure 2-6

The G-8N • 15

Attaching the Counterweight Bar and Counterweight

The last item to be mounted before the telescope tube is the counterweight bar
and counterweight. Used to balanced the telescope, the counterweight bar attaches
to the opposite side of the mount as the telescope. To install the counterweight bar:

1. Retract the counterweight bar lock nut by turning it counterclockwise. This
will expose the threads on the end of the counterweight bar.

2. Thread the counterweight bar into the mount completely. Once again, it
threads into the mount opposite the telescope (see figure 2-7).

3. Tighten the counterweight bar lock nut fully for added support.

The counterweight bar is now installed. With the counterweight bar in place,
you are ready to attach the counterweight.

1. Lock the DEC clamp to hold the mount in place.

2. Remove the safety thumbscrew on the end of the counterweight bar.

3. Loosen the set screw on the counterweight itself so that the central hole of
the counterweight is unobstructed.

4. Slide the counterweight onto the counterweight bar (see figure 2-7).

5. Tighten the set screw on the counterweight to hold it in position.

6. Replace the safety thumbscrew on the end of the counterweight bar. The
thumbscrew will prevent the counterweight from sliding off the bar should
they ever become loose.

With the mount fully assembled, you are ready to attach the telescope to the mount.

Counterweight Bar

Lock Nut

Counterweight Bar

Counterweight

Counterweight Lock
Screw

16 • The C150-HD

Counterweight
Safety Screw

Figure 2-7

Attaching the Telescope
to the Mount (For G-8N)

NOTE: Never loosen any of the knobs on the telescope tube or mount. Also, be sure

Before you attach the optical tube, fully tighten the right ascension and declination
clamps. This will prevent the telescope from moving suddenly once attached to the
mount.

1 Locate the mounting bracket from the box containing the equatorial mount head.
2 Attach the mounting bracket to the tube rings so that the tappered (narrow) end is

against the bottom of the tube rings.
3 Loosen the hand knob on the side of the CG-5 mount.
4 Slide the mounting bracket that is attached to the bottom of the tube rings into

the reccess on the top of the mounting platform (see figure 2-8).
5 Tighten the telescope mounting screw on the CG-5 mount to hold the telescope

in place.
6 Hand tighten the mounting platform safety screw until the tip touches the side of

the mounting bracket (see figure 2-5).

that the open end of the telescope is pointing away from the ground at all
times.

Mounting Bracket

Mounting Platform

Telescope Mounting

Screw

Tube Rings

Figure 2-8

This illustration shows the correct mounting procedure for the optical tube onto the CG-5
mount. The mounting bracket has been attached to the telescope tube rings and is ready
to attach to the CG-5 mount.

The G-8N • 17

Attaching the Telescope
to the Mount (For C150­HD)

Before you attach the optical tube, make sure that the declination and right ascension
clamps are tight. The optical tube attaches to the mount via two rings that are
mounted on the tube of the telescope. To mount the telescope tube:

1. Loosen the knobs on the side of the rings. This will allow you to slide the mount­ing rings the length of the optical tube.

2. Locate the two holes on either end of the CG-4 mounting platform.

3. Hold the telescope up to the mount and slide the mounting rings until they are over
the holes on the mounting platform.

4. Place the flat portion of the ring over the mount so that the hole in the ring is over
the holes of the mounting platform.

5. Thread the mounting screws underneath the mounting platform to secure the rings.

Tighten the knobs on the side of the mounting rings to prevent the telescope from
sliding forward or backward. These can be loosened later to reposition the telescope
during the balancing process.

Mounting Platform

Tube Rings

18 • The C150-HD

Figure 2-8A

This illustration shows the correct mounting procedure for the C150-HD optical tube onto
the CG-4 mount.

Removing the Lens
Cap

The G-8N lens cover has a 1-1/2" cap covering an aperture stop that is offset from
the center. To utilize the aperture stop, leave the telescope cover on the front of the
tube and remove only the small aperture stop cap from the front of the cover. This is
useful when observing very bright objects, like the full moon. The aperture stop
reduces the amount of light entering the tube resulting in better resolution. Do not

use the aperture stop to view the Sun unless using a proper solar filter.

Balancing the Telescope
in R.A.

To eliminate undue stress on the mount, the telescope should be properly
balanced around the polar axis. In addition, proper balancing is crucial for
accurate tracking if using an optional motor drive. To balance the mount:

1. Release the R.A. Clamp and position the telescope off to one side of the
mount (make sure that the mounting bracket screw is tight). The counter­weight bar will extend horizontally on the opposite side of the mount (see
figure 2-9).

2. Release the telescope — GRADUALLY — to see which way the telescope
“rolls.”

3. Loosen the set screw on the counterweight.

4. Move the counterweight to a point where it balances the telescope (i.e., it
remains stationary when the R.A. clamp is released).

5. Tighten the set screw to hold the counterweight(s) in place.

These are general balance instructions and will reduce undue stress on the
mount. When taking astrophotographs, this balance process should be done
for the specific area at which the telescope is pointing.

Figure 2-9

The telescope should be balanced after all the standard accessories (i.e., finderscope,
eyepiece, etc.) have been attached to the telescope. The correct procedure for attaching
these accessories is discussed latr in this section.

The G-8N • 19

Balancing the Telescope
in DEC

The telescope should also be balanced on the declination axis to prevent any
sudden motions when the DEC clamp is released. To balance the telescope in
DEC:

1. Release the R.A. clamp and rotate the telescope so that it is on one side of
the mount (i.e., as described in the previous section on balancing the
telescope in R.A.).

2. Lock the R.A. clamp to hold the telescope in place.

3. Release the DEC clamp and rotate the telescope until the tube is parallel to
the ground (see figure 2-10).

4. Release the tube — GRADUALLY — to see which way it rotates around
the declination axis. DO NOT LET GO OF THE TELESCOPE TUBE

COMPLETELY!

5. Loosen the screws that hold the telescope tube inside the mounting rings
and slide the telescope either forwards or backwards until it remains
stationary when the DEC clamp is released.

6. Tighten the tude ring screws firmly to hold the telescope in place.

Like the R.A. balance, these are general balance instructions and will reduce
undue stress on the mount. When taking astrophotographs, this balance
process should be done for the specific area at which the telescope is pointing.

20 • The C150-HD

Figure 2-10

As with R.A., the telescope should be balanced in DEC after all the standard accessories
(i.e., finderscope, eyepiece, etc.) have been attached to the telescope.

Adjusting the Mount
in Altitude

For the purpose of polar alignment, there are two directions in which the mount can
be adjusted; vertically, which is called altitude and horizontally, which is called
azimuth. There are several ways to align on the celestial pole, many of which are
discussed later in this manual. This section simply covers the correct movement of
the mount during the polar alignment process. To adjust the mount in altitude (i.e.,
raise or lower the angle of the polar axis), turn the altitude adjustment screw:

• Turning the knob clockwise increases the angle at which the polar axis is

pointing

• Turning the handle counterclockwise lowers the angle at which the polar

axis is pointing.

The latitude adjustment on the CG-4 and CG-5 mount has a range of 40°, starting at
20° going up to 60°.

Adjusting the Mount
in Azimuth

For rough adjustments in azimuth, simply pick up the telescope and tripod
and move it. For fine adjustments in azimuth:

1. Turn the azimuth adjustment screws located on either side of the azimuth

housing at the base of the mount. While standing behind the telescope, the
knobs are on the front of the mount.

• Turning the right adjustment knob clockwise moves the mount toward
the right.

• Turning the left adjustment knob clockwise moves the mount to the left.

Both screws push off of the peg on the tripod head, which means you may
have to loosen one screw while tightening the other. The screw that holds the
equatorial mount to the tripod may have to be loosened slightly.

Figure 2-11

The G-8N • 21

Disassembling and
Transporting Your
Telescope

The entire telescope and mount is light enough to pick up and carry outside for a
casual observing session. If, however, you want to transport your telescope to a
remote observing location, you must partially disassemble it. Here’s how:

1. Remove the telescope from the equatorial mount. Return it to the shipping
carton to ensure safe transportation.

2. Remove the three wing bolts that hold the accessory tray to the tripod.

3. Pull the accessory tray off the bracket.

4. Thread the wing bolts back onto the accessory tray once they are removed
from the bracket. This will eliminate the possibility of losing them.

5. Fold the tripod legs together and you are ready to transport your telescope.

The equatorial mount does NOT have to be removed if you are transporting
the telescope yourself. However, you may want to remove the counterweight
from the counterweight bar to lighten the mount.

If you are shipping the telescope via a common carrier, you should completely
disassemble the telescope and return all parts to their original shipping
container.

Storing Your Telescope

When not in use, your Celestron telescope can be left fully assembled and set up.
However, all lens and eyepiece covers should be put back in place. The opening to
the focuser must also be covered. This will reduce the amount of dust build-up on
the optical surfaces and reduce the number of times you need to clean the instru­ment. You may want to return everything to its original shipping container and
store all the parts there. If this is the case, all optical surfaces should still be covered
to prevent dust build-up.

Now that you have completed assembling your telescope, you are ready to begin
attaching the accessories.

22 • The C150-HD

Installing the
Finderscope

To install the finderscope onto the telescope you must first mount the finderscope
through the finder bracket and then attach it to the telescope. Toward the front of
the telescope tube, near the focusing assembly, there is a small bracket with a set
screw in it. This is where the finderscope bracket will be mounted. To install the
finderscope:

1. Slide the rubber O-ring over the eyepiece end of the finderscope and
roll it 2/3 of the way up the finderscope.

2. Insert the eyepiece end of the finderscope through the bracket until the
O-ring presses tightly between the finder and the inside of the bracket.

3. Tighten the adjustment screws until they make contact with the
finderscope body.

4. Locate the mounting bracket near the front (open) end of the telescope.

5. Loosen the set screw on the mounting bracket on the telescope.

6. Slide the finder bracket (attached to the finderscope) into the mounting
bracket on the telescope.

7. The finderscope bracket will slide in from the back. The finderscope
should be oriented so that the objective lens is toward the front (open)
end of the telescope (see figure 2-12).

8. Tighten the set screw on the mounting bracket to hold the finderscope
in place.

Figure 2-12

The G-8N • 23

Installing the Eye­piece

The eyepiece, or ocular as it is also called, is an optical element that magnifies
the image focused by the telescope. Without the eyepiece it would be impos­sible to use the telescope visually. The eyepiece fits directly into the eyepiece
holder. To attach an ocular:

1. Loosen the set screw on the eyepiece holder so that it does not obstruct the
inner diameter of the eyepiece holder.

2. Slide the chrome portion of the eyepiece into the eyepiece holder.

3. Tighten the set screw to hold the eyepiece in place.

To remove the eyepiece, loosen the set screw on the eyepiece holder and slide
the eyepiece out. You can replace it with another ocular.

Eyepieces are commonly referred to by focal length which is printed on the
eyepiece barrel. The longer the focal length (i.e., the larger the number) the
lower the eyepiece power and the shorter the focal length (i.e., the smaller the
number) the higher the magnification. Generally, you will use low-to-moder­ate power when viewing. For more information on how to determine power,
see the section on “Calculating Magnification.”

In addition, eyepieces are also referred to by barrel diameter. The C150-HD and G­8N use eyepieces with a barrel diameter of 1-1/4".

Once the telescope is fully assembled, tighten the bolts that hold the tripod legs to
the tripod head and the bolts that adjust the tripod height. Check these bolts
periodically to ensure they are tight. The first check should be done 24 hours after
initial assembly.

24 • The C150-HD

Figure 2-13

Technical
Specifications

These specifications are approximate and subject to change without notice.

Below is pertinent technical information on your G-8N and C150-HD telescope that
you may find useful.

G-8N C150-HD
Optical System: Newtonian Reflector Newtonian Reflector
Aperture: 200mm (8") 150mm (6")
Focal Length: 1000mm (40") 750mm (30")
Highest Useful Power: 480x 360x
Resolution (arc seconds): 0.58 .77
Light Gathering Power: 816 459
Limiting Visual Magnitude: 14 13.5
Secondary Obstruction 2.9" 2.2"
% of Primary Surface Area 13.1% 13.4%
f/ratio: f/5 f/5
Length: 19.75" 14.5"
Weight
Optical Tube: 15.5 lb. 8.5 lb.
With Tripod: 30.5 lb. 25lb.

The G-8N • 25

TELESCOPE BASICS

Once your telescope has been fully assembled and the accessories attached,
you are ready to take a look. This section deals with basic telescope operation.

Image Orientation

The Newtonian optical system produces an upside down image. This will
only affect your terrestrial observations. For celestial viewing, star charts can
be made to match the view in the telescope by rotating the chart 180° about the
center. The view through the finder is also inverted.

Actual Veiw

Newtonian View

Figure 3-1

The figure illustrate the image orientation of a Newtonian telescope. Top is the actual
orientation while below is the image seen through the telescope. The finderscope
produces an inverted (upside-down and backwards)image.

26 • Telescope Basic

Focusing

To focus your telescope, simply turn the focus knob located directly below the
eyepiece holder (see figure 2-13). Turning the knob clockwise allows you to
focus on an object that is farther than the one you are currently observing.
Turning the knob counterclockwise from you allows you to focus on an object
closer than the one you are currently observing.

In addition to understanding how the focusing mechanism works, there are a
few focusing hints that should be remembered when using any optical instru­ment.

• Never look through glass. Glass found in household windows is optically
imperfect, and as a result, may vary in thickness from one location to the
next. This inconsistency can and will affect the ability to focus your
telescope. In most cases you will not be able to achieve a truly sharp focus.
In some cases, you may actually see a double image.

• Never look across or over objects that are producing heat waves. This
includes asphalt parking lots on hot summer days or building roof tops.

• Hazy skies, fog and mist can also make it difficult to focus. The amount of
detail that can be seen under these conditions will be greatly reduced.

• When using your telescope as a telephoto lens, the split screen focuser of
the 35mm camera may “black out.” This is common with all long focal
length lenses. If this does happen, use the ground glass portion of your
focusing screen. To achieve a very sharp focus, consider using a focusing
magnifier which is readily available from your local camera store.

• If you wear corrective lenses (specifically glasses), you may want to remove
them when observing with an eyepiece attached to the telescope. However,
when using a camera you should always wear corrective lenses to ensure
the sharpest possible focus. If you have astigmatism, corrective lenses must
be worn at all times.

Telescope Basics • 27

Aligning the Finder

Accurate alignment of the finder makes it easy to find objects with the telescope,
especially celestial objects. To make aligning the finder as easy as possible, this
procedure should be done in the daytime when it is easy to find and identify objects.
The finderscope has a spring-loaded adjustment screw that puts pressure on the
finderscope while the remaining screws are used to adjust the finder horizontally
and vertically. To align the finder:

1 Choose a target that is in excess of one mile away. This eliminates any

possible parallax effect between the telescope and finder.
2 Release the R.A. and DEC clamps and point the telescope at your target.
3 Center your target in the main optics of the telescope. You may have to

move the telescope slightly to center it.
4 Adjust the screw on the finder bracket that is on the right (when looking

through the finder) until the cross hairs are centered horizontally on the

target seen through the telescope.
5 Adjust the screw on the top of the finder bracket until the cross hairs are

centered vertically on the target seen through the telescope.
Image orientation through the finder is inverted (i.e., upside down and back-

wards left-to-right). This is normal for any finder that is used straight-through.
Because of this, it may take a few minutes to familiarize yourself with the
directional change each screw makes on the finder.

28 • Telescope Basic

Your First Look

With the telescope fully assembled and all the accessories attached you are

ready for your first look. Your first look should be done in the daytime when it

is easier to locate the locking clamps and slow motion adjustment knobs. This

will help to familiarize you with your telescope, thus making it easier to use at

night.

Daytime Observing

1. Begin by finding a distant object that is fairly bright.

2. Insert a low power eyepiece (one with a large focal length) into the tele­scope.

3. Release the R.A. and DEC clamps and point the telescope at the object you
selected.

4. Locate the object in your finder and lock the R.A. and DEC clamps.

5. Use the slow motion knobs to center the object in the field of the finder.

6. Once centered, look through your telescope and the object will be there (if you
aligned the finder first).

Try using different optional eyepieces to see how the field changes with
various magnifications.

WARNING ! NEVER POINT YOUR TELESCOPE AT THE SUN UNLESS YOU

HAVE THE PROPER SOLAR FILTER. PERMANENT AND IRRE­VERSIBLE EYE DAMAGE MAY RESULT AS WELL AS DAMAGE TO
YOUR TELESCOPE. ALSO, NEVER LEAVE YOUR TELESCOPE
UNATTENDED DURING A DAYTIME OBSERVING SESSION, ESPE­CIALLY WHEN CHILDREN ARE PRESENT.

Telescope Basics • 29

Nighttime Observing

Looking at objects in the sky is quite different than looking at objects on Earth.
For one, many objects seen in the daytime are easy to see with the naked eye
and can be located by using landmarks. In addition, objects on the ground are
stationary, or at least for the most part. In the night sky you will see a tremen­dous amount of stars that are not visible to the naked eye and the only way to
find objects (at least initially) is by using other stars to guide you there. This
method of finding objects, known as star hopping, is very accurate. Yet it
requires a fair amount of time to learn the stars well enough so as to guide you
to other objects. Furthermore, the stars appear to drift out of the field of view.
This is due to the Earth’s rotation. In fact, anything in the sky, day or night,
will drift out unless the telescope has been polar aligned and the optional
clock drive is running. There is more on this in the section on “Polar Align­ment.”

1. Orient the telescope so that the R.A. or polar axis is pointing north, as
close to true north as possible. You can use a landmark that you know
faces north to get you in the general direction.

2. Adjust the mount until the latitude indicator points to the latitude from
which you are observing.

3. Insert an eyepiece into the telescope. It should be a low power eyepiece
(i.e., one with a large number on the side) to give you the widest field
possible.

4. Turn the motor drive on (if you are using one).

5. Release the right ascension and declination clamps and point the tele­scope at the desired target. The Moon or one of the brighter planets is an
ideal first target.

6. Locate the object in the finder, center it, and then look through the tele­scope.

7. Turn the focus knob on your G-8N until the image is sharp.

8. Take your time and study your subject. If looking at the Moon, look for
small detail in the craters.

That’s all there is to using your Celestron Newtonian telescope. However, don’t
limit your view of an object to a single eyepiece. After observing an object for a few
minutes, try using a different optional eyepiece, perhaps a more powerful one. This
gives you an idea of how the field of view changes. Center your target and refocus.
Once again, if looking at the Moon you will be looking at a few craters at one time.
Use the slow motion knobs to scan the lunar surface.

30 • Telescope Basic

Calculating
Magnification

As implied in the previous section, you can change the power of your
Celestron telescope just by changing the eyepiece (ocular). To determine the
magnification for your telescope, simply divide the focal length of the telescope
(1000mm) by the focal length of the eyepiece you are using. In equation format, the
formula looks like this:

Focal Length of Telescope (mm)

Magnification = —————————————————

Focal Length of Eyepiece (mm)

Let’s take an example to see how this formula works. If you were using the
standard 20mm eyepiece supplied with your C150-HD or G-8N, you simply divide
the focal length of the telescope (1000mm) by the focal length of the eyepiece
(20mm). 1000mm divided by 20mm yields a magnification of 50 power.

Although the power is variable, each instrument has a limit to the highest
useful magnification. The general rule is that 60 power can be used for every
inch of aperture. For example, the G-8N has a mirror diameter of 8". Multiply­ing 8 by 60 gives a maximum useful magnification of 480 power. Although
this is the maximum useful magnification, most observing is done in the range
of 20 to 35 power for every inch of aperture, which for the G-8N is between 160
and 280 power.

Determining Field of
View

Determining the field of view is important if you want to get an idea of the
angular size of the object you are observing. To calculate the actual field of
view, divide the apparent field of the eyepiece (supplied by the eyepiece
manufacturer) by the magnification. As you can see, before you determine the
field of view, you must first calculate the magnification. In equation format,
the formula looks like this:

Apparent Field of Eyepiece

True Field = ———————————————

Magnification

Using the example we started with above, we can determine the field of view
using the same 20mm eyepiece. The 20mm eyepiece has an apparent field of
view of approximately 52°. Divide the 52° by the magnification, which is 50
power. This yields an actual field of 1.04°, or a little more than a degree.

This formula gives you the true field of view in degrees. To convert degrees to
feet at 1,000 yards, which is more commonly used for terrestrial viewing,
simply multiply by 52.5. Continuing with our example, 1.04 times 52.5
produces a field size of 55 feet at 1,000 yards.

The apparent field of each eyepiece that Celestron manufactures is found in
the Celestron accessory catalog (#93685).

Telescope Basics • 31

ASTRONOMY BASICS

This section deals with observational astronomy in general. It includes infor­mation on the night sky, polar alignment, and using your telescope for astro­nomical observations.

The Celestial Coordi­nate System

In order to help find objects in the sky, astronomers use a celestial coordinate
system which is similar to our geographical coordinate system here on Earth.
The celestial coordinate system has poles, lines of longitude and latitude, and
an equator. For the most part, these remain fixed against the background
stars.

The celestial equator runs 360 degrees around the Earth and separates the
northern celestial hemisphere from the southern. Like the Earth’s equator it
bears a reading of zero degrees. On Earth this would be latitude. However, in
the sky this is now referred to as declination, or DEC for short. Lines of
declination above and below the celestial equator are labeled for their angular
distance from the equator. The lines are broken down into degrees, minutes,
and seconds of arc. Declination readings south of the equator carry a minus
sign (-) in front of the number and those north are often preceded by a plus sign
(+).

The celestial equivalent of longitude is called Right Ascension, or R.A. for
short. Like the Earth’s lines of longitude, they run from pole to pole and are
evenly spaced 15 degrees apart. Although the longitude lines are separated by
an angular distance, they are also a measure of time. Each line of longitude is
one hour apart from the next. Since the Earth rotates once every 24 hours,
there are 24 lines total. The R.A. coordinates are marked off in units of time.
It begins with an arbitrary point in the constellation of Pisces designated as 0
hours, 0 minutes, 0 seconds. All other points are designated by how far (i.e.,
how long) they lag behind this coordinate after it passes overhead moving
toward the west.

32 • Astronomy Basics

Your Celestron telescope comes equipped with setting circles that translate
the celestial coordinates into a precise location for the telescope to point. The
setting circles will not work properly until you have polar aligned the telescope
and set the R.A. setting circle. Note that the process of polar alignment sets
the declination setting circle.

90

60

Declination

30

22

23

0

1

3

2

6

5

4

Right
Ascension

Figure 4-1

Motion of the Stars

Like the Sun, the stars also appear to move across the sky. This motion is caused
by the Earth’s rotation. For observers in the northern hemisphere, all stars appear
to move around the north celestial pole. For observers in the southern hemisphere,
all stars appear to move around the south celestial pole. This means that over a 24­hour period, any given star will scribe out a complete circle around its respective
celestial pole. The farther you move away from the celestial pole, the larger this
circle becomes and is largest at the celestial equator. Stars near the celestial
equator rise in the east and set in the west. However, stars near the celestial poles
are always above the horizon. They are said to be circumpolar because they don’t
rise and set. You will never see the stars complete one circle because the sunlight
during the day washes out the starlight. However, part of this circular motion of
stars in this region of the sky can be seen by setting up a camera on a tripod and
opening the shutter for a couple of hours. The processed film will reveal circular
arcs that are centered on the pole. This information will be useful for certain
methods of polar alignment.

Figure 4-2

All stars appear to rotate around the celestial poles. However, the appearance of this
motion varies depending on where you are looking in the sky. Near the north celestial
pole the stars scribe out recognizable circles centered on the pole (1). Stars near the
celestial equator also follow circular paths around the pole. But, the complete path is
interrupted by the horizon. These appear to rise in the east and set in the west (2).
Looking toward the opposite pole, stars curve or arc in the opposite direction scribing a
circle around the opposite pole (3).

Astronomy Basics • 33

Polar Alignment

In order for the telescope to track the stars it must meet two criteria. First,
you need a drive motor that will move at the same rate as the stars. For the G-8N
there are two optional motor drives (#93518 and #93523) that can be fitted to it. For
the C150-HD there are also two optional motor drives (#93517 and #93522). The
second thing you need is to set the telescope’s axis of rotation so that it tracks in the
right direction. Since the motion of the stars across the sky is caused by the Earth’s
rotation about its axis, the telescope’s axis must be made parallel to the Earth’s axis.

Polar alignment is the process by which the telescope’s axis of rotation is
aligned (made parallel) with the Earth’s axis of rotation. Once aligned, a
telescope with a clock drive will track the stars as they move across the sky.
The result is that objects observed through the telescope will appear stationary
(i.e., they will not drift out of the field of view). If your telescope does not use a
motor drive, all objects in the sky (day or night) will drift out of the field. This
apparent motion is caused by the Earth’s rotation. Even if you are not using a
motor drive, polar alignment is still desirable since it will reduce the number of
corrections needed to follow an object and will limit all corrections to one axis
(R.A.). There are several methods of polar alignment, all of which work on a
similar principle, but are performed somewhat differently. Each method will be
considered separately, beginning with the easier methods and working to the
more difficult, but more precise.

Although there are several methods mentioned here, you will never use all of
them during one particular observing session. Instead, you may use only one
if it is a casual observing session. Or, if you plan on astrophotography, you
may use two methods — one for rough alignment followed by a more accurate
method.

Definition: The polar axis is the axis around which the telescope rotates when moving the

telescope in right ascension. This axis remains stationary as the telescope
moves in right ascension and declination.

Figure 4-3

When the telescope’s axis of rotation is parallel to the Earth’s axis, stars viewed
through the telescope appear stationary when using a motor drive.

34 • Astronomy Basics

Finding the Pole

Figure 4-4

For each hemisphere, there is a point in the sky around which all the other
stars appear to rotate. These points are called the celestial poles and are
named for the hemisphere in which they reside. For example, in the northern
hemisphere all stars move around the north celestial pole. When the
telescope’s polar axis is pointed at the celestial pole, it is parallel to the
Earth’s rotational axis.

Many of the methods of polar alignment require that you know how to find the
celestial pole by identifying stars in the area. For those in the northern
hemisphere, finding the celestial pole is relatively easy. Fortunately, we have a
naked eye star less than a degree away. This star, Polaris, is the end star in
the handle of the Little Dipper (see figure 4-5). Since the Little Dipper (technically
called Ursa Minor) is not one of the brightest constellations in the sky, it may be
difficult to locate, especially from urban areas. If this is the case, use the two end
stars in the bowl of the Big Dipper. Draw an imaginary line through them (about
five times the distance between these two stars) toward the Little Dipper. They
will point to Polaris. The position of the Big Dipper will change during the year
and throughout the course of the night (see figure 4-4). When the Big Dipper is
difficult to locate, try using Cassiopia.

The position of the Big
Dipper changes through­out the year and through­out the night.

Definition: The north celestial pole is the point in the northern sky around which all stars

Observers in the southern hemisphere are not as fortunate as those in the
northern hemisphere. The stars around the south celestial pole are not nearly
as bright as those around the north. The closest star that is relatively bright is
Sigma Octantis. This star is just within naked eye limit (magnitude 5.5) and
lies 59 arc minutes from the pole. For more information about stars around the
south celestial pole, please consult a star atlas.

While it may seem that pointing at the pole star produces a parallax effect,
especially for observers near the equator, this effect is negligible since Polaris
is so far away.

appear to rotate. The counterpart in the southern hemisphere is referred to as
the south celestial pole.

Figure 4-5

The two stars in the front of the bowl of the Big Dipper point to Polaris which is less
than one degree from the true (north) celestial pole. Cassiopia, the “W” shaped
constellation is on the opposite side of the pole from the Big Dipper. The North
Celestial Pole (N.C.P.) is marked by the “+” sign.

Astronomy Basics • 35

Latitude Scales

The easiest way to polar align a telescope is with a latitude scale. Unlike
other methods that require you to find the celestial pole by identifying certain
stars near it, this method works off of a known constant to determine how high
the polar axis should be pointed. The latitude range varies depending upon the
telescope you own. The range for the CG-4 and CG-5 and is 40°.

The constant, mentioned above, is a relationship between your latitude and the
angular distance the celestial pole is above the northern (or southern) horizon.
The angular distance from the northern horizon to the north celestial pole is
always equal to your latitude. To illustrate this, imagine that you are standing
on the north pole, latitude +90°. The north celestial pole, which has a declina­tion of +90°, would be directly overhead (i.e., 90 above the horizon). Now let’s
say that you move one degree south. Your latitude is now +89° and the
celestial pole is no longer directly overhead. It has moved one degree closer
toward the northern horizon. This means the pole is now 89° above the
northern horizon. If you move one degree further south, the same thing
happens again. As you can see from this example, the distance from the
northern horizon to the celestial pole is always equal to your latitude.

If you are observing from Los Angeles, which has a latitude of 34°, then the
celestial pole would be 34° above the northern horizon. All a latitude scale
does then is to point the polar axis of the telescope at the right elevation above
the northern (or southern) horizon. To align your telescope:

1. Point your telescope due north. Use a landmark that you know faces
north.

2. Level the tripod by raising or lowering the legs as needed. There is a
bubble level built into the CG-5 mount for this purpose.

3. Adjust the telescope mount in altitude until the latitude indicator points to
your latitude.

This method can be done in daylight, thus eliminating the need to fumble
around in the dark. Although this method does NOT put you directly on the
pole, it will limit the number of corrections needed when tracking an object. It
will also be accurate enough for short exposure prime focus planetary photog­raphy (a couple of seconds) and short exposure piggyback astrophotography.

36 • Astronomy Basics

Pointing at Polaris

This method utilizes Polaris as a guidepost to the celestial pole. Since Polaris
is less than a degree from the celestial pole, many amateurs simply point the
polar axis of their telescope at Polaris. Although this is by no means a perfect
alignment, it is close. To align using this method:

Align the finderscope with the main optical tube as described in the "Aligning
the Finder" section earlier in the manual.

1 Set the telescope up so that the polar axis is pointing north and the

counterweight shaft is rotated towards the ground.

2 Release the DEC clamp and move the telescope so that the optical tube is

directly over the polar axis (see figure 4-6).

3 Move the mount in altitude and/or azimuth until Polaris is in the field of

view of the finder. Rough azimuth adjustments can be made by moving the
tripod .

4 Center Polaris using the fine altitude and azimuth controls (refer to figure 2-

5). Remember, do not move the telescope in R.A. or DEC. You

want to adjust the direction the mount is pointing and you are
using the telescope to see where the mount is pointing.

5 Once Polaris is in the finder it should also be centered in the telescope. If

not, use the fine adjustment controls to center Polaris in the telescope
field.

6 Rotate the Declination circle, just above the counterweight shaft, to read

90°. Do not move the Declination circle by hand after it is set.

Figure 4-6

Astronomy Basics • 37

Declination Drift

This method of polar alignment allows you to get the most accurate alignment
on the celestial pole and is required if you want to do long exposure deep-sky
astrophotography through the telescope. The declination drift method requires
that you monitor the drift of selected guide stars. The drift of each guide star
tells you how far away the polar axis is pointing from the true celestial pole and
in what direction. Although declination drift is quite simple and straightforward,
it requires a great deal of time and patience to complete when first attempted.
The declination drift method should be done after any one of the previously
mentioned methods has been completed.

To perform the declination drift method you need to choose two bright stars.
One should be near the eastern horizon and one due south near the meridian.
Both stars should be near the celestial equator (i.e., 0° declination). You will
monitor the drift of each star one at a time and in declination only. While
monitoring a star on the meridian, any misalignment in the east-west direction
will be revealed. While monitoring a star near the east/west horizon, any
misalignment in the north-south direction will be revealed. As for hardware,
you will need an illuminated reticle ocular to help you recognize any drift. For
very close alignment, a Barlow lens is also recommended since it increases
the magnification and reveals any drift faster.

When looking due south with the scope on the side of the mount, insert the
diagonal so it points straight up. Insert a cross hair ocular and align the cross
hairs to be parallel to declination and right ascension motion.

First choose your star near where the celestial equator and the meridian meet.
The star should be approximately ±1/2 hour of the meridian and ±5 degrees of
the celestial equator. Center the star in the field of your telescope and monitor
the drift in declination.

• If the star drifts south, the polar axis is too far east.

• If the star drifts north, the polar axis is too far west.

Make the appropriate adjustments to the polar axis to eliminate any drift.
Once you have managed to eliminate all drift, move to the star near the eastern
horizon. The star should be 20 degrees above the horizon and ± 5 degrees off
of the celestial equator.

• If the star drifts south, the polar axis is too low.

• If the star drifts north, the polar axis is too high.

Once again, make the appropriate adjustments to the polar axis to eliminate
any drift. Unfortunately, the latter adjustments interact with the prior adjust­ments ever so slightly. So, repeat the process again to improve the accuracy
checking both axes for minimal drift. Once the drift has been eliminated, the
telescope is very accurately aligned. You will now be able to do prime focus
deep-sky astrophotography for long periods.

NOTE: If the eastern horizon is blocked, you may choose a star near the western

38 • Astronomy Basics

horizon. However, you will have to reverse the polar high/low error directions. If
using this method in the southern hemisphere, the procedure is the same as
described above. However, the direction of drift is reversed.

Aligning the R.A.
Setting Circle

Polar Alignment Finders

There are two finders specifically designed for polar alignment that can be used
with the CG-4 and CG-5 mounts. These finders can be purchased as optional
accessories for the C150-HD and G-8N. The first finder, known as the 7x50 Polaris
finder (#51614), is used as a regular finder.

The second finder is the polar axis finderscope (#94221). Its sole purpose is polar
alignment and can NOT be used to find objects in the telescope. Both these finders
work on the same principle, but their methods of operation are slightly different.
These methods are generally easier than those already described and they are fairly
accurate. For more information on both these finderscopes, refer to the Optional
Accessories section of this manual or ask for the Celestron accessory catalog
(#93685).

Before you can use the setting circles to find objects in the sky you need to align the
R.A. setting circle. The declination setting circle is aligned during the polar
alignment process. In order to align the R.A. setting circle you will need to know
the names of a few of the brightest stars in the sky . If you don’t, they can be
learned by using the Celestron Sky Maps (#93722) or consulting a current as­tronomy magazine. To align the R.A. setting circle:

1. Locate a bright star near the celestial equator. The farther you are from the
celestial pole the better your reading on the R.A. setting circle will be. The
star you choose to align the setting circle with should be a bright one whose
coordinates are known and easy to look up. (For a list of bright stars to align
the R.A. setting circle, see the list at the back of this manual.)

2. Center the star in the finder.

3. Look through the main telescope and see if the star is in the field. If not, find it
and center it.

4. Start the optional motor drive so that it will track the star. If you are not using
a motor drive the star will start to drift out of the field and you will need to
center it again before setting the R.A. circle.

5. Look up the coordinates of the star.

6. Rotate the circle until the proper coordinates line up with the R.A. indicator
(the zero mark on the vernier scale). The R.A. setting circle should rotate
freely.

As mentioned above, the declination setting circle is aligned during the pro­cess of polar alignment. There is no need to align it in the same manner as
the R.A. setting circle.

Once you have finished this process you are ready to use the setting circles to
locate objects in the night sky. See the section on “Using the Setting Circles”
for specific information.

Astronomy Basics • 39

CELESTIAL OBSERVING

Observing the Moon

With your telescope set up, you are ready to use it for celestial observing.
This section covers visual observing of both solar system and deep-sky
objects.

In the night sky, the Moon is a prime target for your first look because it is
extremely bright and easy to find. Often, it is a temptation to look at the Moon
when it is full. At this time, the face we see is fully illuminated and its light can
be overpowering. In addition, little or no contrast can be seen during this
phase.

One of the best times to observe the Moon is during its partial phases (around
the time of first or third quarter). Long shadows reveal a great amount of detail
on the lunar surface. At low power you will be able to see most of the lunar
disk at one time. Change to higher power (magnification) to focus in on a
smaller area. Keep in mind that if you are not using an optional motor drive,
the rotation of the Earth will cause the Moon to drift out of your field of view.
You will have to manually adjust the telescope to keep the Moon centered.
This effect is more noticeable at higher power.

If you are using a motor drive and have polar aligned, the Moon will remain
centered. Consult your local newspaper or a current astronomy magazine to
find out when the Moon will be visible. Try using filters to increase contrast
and bring out more detail on the lunar surface.

Observing the
Planets

Other easy targets in the night sky include the five naked eye planets. You
can see Venus go through its lunar-like phases. Mars can reveal a host of
surface detail and one, if not both, of its polar caps. You will be able to see
the cloud belts of Jupiter and the great Red Spot (if it is visible at the time you
are observing). In addition, you will also be able to see the moons of Jupiter as
they orbit this gas giant. Saturn with its beautiful ring system and Cassini's
division are easily visible at moderate power. All you need to know is where to
look. Most astronomy publications tell where the planets can be found in the
sky each month.

Figure 5-1

This scanned drawing of Jupiter provides a good representation of what you can expect
to see with moderate magnification during good seeing conditions. The large, bright
cloud belts should be immediately obvious. Smaller, faint belts become visible with
practice and experience.

40 • Celestial Observing

Observing the
Sun

WARNING: Never project an image of the Sun through the telescope. Because of

Although overlooked by many amateur astronomers, solar observation is both
rewarding and fun. However, because the Sun is so bright, special precautions
must be taken (always use the proper solar filter) when observing our star so as not
to damage your eyes or your telescope.

the folded optical design, tremendous heat build-up will result inside
the optical tube. This can damage the telescope and/or any accesso­ries attached to the telescope.

SOLAR OBSERVING HINTS

• The best time to observe the Sun is in the early morning or late afternoon
when the air is cooler.

• To locate the Sun without a finder, watch the shadow of the telescope tube
until it forms a circular shadow.

Observing Deep-Sky
Objects

Deep-sky objects are simply those objects outside the boundaries of our solar
system. They include star clusters, planetary nebulae, diffuse nebulae, double
stars, and other galaxies outside our own Milky Way. The Celestron Sky
Maps (#93722) can help you locate the brightest deep-sky objects.

Most deep-sky objects have a large angular size. Therefore, low-to-moderate
power is all you need to see them. Visually, they are too faint to reveal any color
seen in long exposure photographs. Instead, they have a black and white appear­ance. And, because of their low surface brightness, they should be observed from a
dark sky location. Light pollution around large urban areas washes out most
nebulae making them difficult, if not impossible, to observe. Light Pollution
Reduction filters help reduce the background sky brightness, thus increasing
contrast.

Celestial Observing • 41

Using the Setting Circles

Once the setting circles are aligned you can use them to find any object with known
coordinates.

1. Select an object to observe. Use a seasonal star chart or planisphere to
make sure the object you chose is above the horizon. As you become
more familiar with the night sky, this will no longer be necessary.

2. Look up the coordinates in an atlas or reference book.

3. Move the telescope in declination until the indicator is pointing at the
correct declination coordinate.

4. Move the telescope in R.A. until the indicator points to the correct coordi­nate (do NOT move the R.A. circle). The telescope will track in R.A. as
long as a motor drive is operating and the R.A. clamp is in the locked
position.

5. Look through the finder to see if you have located the object.

6. Center the object in the finder.

7. Look in the main optics using a low power eyepiece; the object should be
there. The telescope will track in R.A. as long as the motor drive is
operating.

8. Repeat the process for each object observed throughout the observing
session.

You may not be able to see fainter objects in the finder. When this happens,
gradually sweep the telescope around until the object is visible.

The declination setting circle is scaled in degrees while the R.A. setting circle
is incremented in minutes with a marker every fifth minute. As a result, the
setting circles will get you close to your target, but not directly on it. Also, the
accuracy of your polar alignment will also affect how accurately your setting
circles read.

At the end of this manual there is a list of deep-sky objects well within reach of
your Celestron telescope.

42 • Celestial Observing

Star Hopping

You can use your setting circles to find these objects (as described earlier in
this manual) or try star hopping. Star hopping is done by using bright stars to
guide you to an object. Here are directions for two popular objects.

The Andromeda Galaxy, M31, is an easy first target. To find M31:

1. Locate the constellation of Pegasus, a large square visible in the fall and winter

months.

2. Start at the star in the northeast corner. The star is Alpha (α)

Andromedae.

3. Move northeast approximately 7°. There you will find two stars of equal

brightness — Delta (δ) and Pi (π) Andromedae — about 3° apart.

4. Continue in the same direction another 8°. There you will find two stars —

Beta (β) and Mu (µ) Andromedae — about 3° apart.

5. Move 3° northwest — the same distance between the two stars— to the

Andromeda galaxy. It is easily visible in the finder.

Figure 5-2

Star hopping to the Andromeda Galaxy is a snap to find since all the stars needed to do
so are visible to the naked eye. Note that the scale for this star chart is different from
the one on the following page which shows the constellation Lyra.

Celestial Observing • 43

Star hopping may take some getting used to since you can see more stars through
the finder than you can see with the naked eye. And, some objects are not visible
in the finder. One such object is M57, the famed Ring Nebula. Here’s how to find
it:

1. Find the constellation of Lyra, a small parallelogram visible in the summer
and fall months. Lyra is easy to pick out because it contains the bright
star Vega.

2. Start at the star Vega — Alpha (α) Lyrae — and move a few degrees
southeast to find the parallelogram. The four stars that make up this
geometric shape are all similar in brightness, making them easy to see.

3. Locate the two southern most stars that make up the parallelogram — Beta (β)
and Gamma (γ) Lyrae (see figure 5-3).

4. Point the finder half way between these two stars.

5. Move about 1/2° toward Beta (β) Lyrae, but remaining on a line that
connects the two stars.

6. Look through the telescope and the Ring Nebula should be in the tele­scope. Its angular size is quite small and, therefore, not visible in the
finder.

Figure 5-3

Although the Ring Nebula lies
between two naked eye stars, it
may take a little time to locate
since it is not visible in the
finder. Note that the scale for
this star chart is different from
the one on the previous page
which shows several constella­tions including Pegasus,
Triangulum, and Andromeda.

These two examples should give you an idea of how to star hop to deep sky objects.
To use this method on other objects, consult any of the star atlases listed at the end
of this book.

44 • Celestial Observing

Viewing Conditions

Viewing conditions affect what you can see through your telescope during an
observing session. Conditions include transparency, sky illumination, and seeing.
Understanding viewing conditions and the affect they have on observing will help
you get the most out of your telescope.

Transparency

Transparency is the clarity of the atmosphere and is affected by clouds,
moisture, and other airborne particles. Thick cumulus clouds are completely
opaque while cirrus can be thin, allowing the light from the brightest stars
through. Hazy skies absorb more light than clear skies making fainter objects
harder to see and reducing contrast on brighter objects. Aerosols ejected into
the upper atmosphere from volcanic eruptions also affect transparency. Ideal
conditions are when the night sky is inky black.

Sky Illumination

General sky brightening caused by the Moon, aurorae, natural airglow, and
light pollution greatly affect transparency. While not a problem for the Moon,
planets, and brighter stars, bright skies reduce the contrast of extended
nebulae making them difficult, if not impossible, to see. To maximize your
observing, limit deep-sky viewing to moonless nights far from the light polluted
skies found around major urban areas. LPR filters enhance deep-sky viewing
from light polluted areas by blocking unwanted light while transmitting light
from certain deep-sky objects. You can, on the other hand, observe planets
and stars from light polluted areas or when the Moon is out.

Seeing

Seeing conditions refer to the stability of the atmosphere and directly effects
the clarity of star images and the amount of fine detail seen in extended
objects like the planets. The air in our atmosphere acts as a lens which bends
and distorts incoming light rays. The amount of bending depends on air
density. Varying temperature layers have different densities and therefore bend
light differently. Light rays from the same object arrive slightly displaced
creating an imperfect or smeared image. These atmospheric disturbances vary
from time-to-time and place-to-place. The size of the air parcels compared to
your aperture determines the “seeing” quality. Under good seeing conditions,
fine detail is visible on the brighter planets like Jupiter and Mars, and stars are
pinpoint images. Under poor seeing conditions, images are blurred and stars
appear as blobs. Seeing conditions are rated on a five-point scale where one
is the worst and five is the best (see figure 5-4). Seeing conditions can be classified
in one of three categories which are based on the cause.

Type 1 seeing conditions are characterized by rapid changes in the image seen
through the telescope. Extended objects, like the Moon, appear to shimmer while
point sources (i.e., stars) appear double. Type 1 seeing is caused by currents
within or very close to the telescope tube. These currents could be caused by a
telescope that has not reached thermal equilibrium with the outdoor surroundings,
heat waves from people standing near the telescope, or heated dew caps. To avoid
the problems associated with Type 1 seeing, allow your telescope approximately
20 to 30 minutes to reach thermal equilibrium. Once adjusted to the outdoor

Celestial Observing • 45

temperature, don’t touch the telescope tube with your hands. When pointing the
telescope, hold the telescope by the star diagonal. If observing with others, make
sure no one stands in front of or directly below the telescope tube.

The images produced by Type 2 seeing conditions don’t move as quickly as those
produced by Type 1 conditions, but the images are quite blurry. Fine detail is lost
and the contrast is low for extended objects. Stars are spread out and not sharp.
The source of Type 2 seeing is the lower atmosphere, most likely heat waves from
the ground or buildings. To avoid the problems associated with Type 2 seeing,
select a good observing site. Specifically, avoid sites that overlook asphalt parking
lots or ploughed fields. Stay away from valleys and shorelines. Instead, look for
broad hilltops or open grassy fields. Stable thermal conditions found near lakes
and atmospheric inversions also tend to produce good seeing. If you can’t get a
better location, wait until the early morning hours when the surroundings are
uniformly cool and the seeing is generally better.

Type 3 seeing conditions are characterized by fast ripples, but sharp images.
In extended objects fine detail is visible, but the images shift around the field.
Stars are crisp points, but they shift small distances rapidly around the field.
The cause of Type 3 seeing is turbulence in the upper atmosphere which
means the observer has less control over it. However, the effects of Type 3
seeing are generally less pronounced than the other two types. You can never
really avoid Type 3 seeing. Your best bet is to wait until moments of steadi­ness. If the seeing is extremely bad, pack up and wait for a better night.

The conditions described here apply to both visual and photographic observa­tions.

Figure 5-4

Seeing conditions directly affect image quality. These drawings represent a point
source (i.e., star) under bad seeing conditions (left) to excellent conditions (right).
Most often, seeing conditions produce images that lie somewhere between these two
extremes.

46 • Celestial Observing

CELESTIAL PHOTOGRAPHY

After looking at the night sky for awhile you may want to try photographing it.
Several forms of celestial photography are possible with your Celestron telescope.
The most common forms of celestial photography, in order of difficulty are: short
exposure prime focus, piggyback, eyepiece projection, and long exposure deep sky.
Each of these is discussed in moderate detail with enough information to get you
started. Topics include the accessories required and some simple techniques. More
information is available in some of the publications listed at the end of this manual.

In addition to the specific accessories required for each type of celestial
photography, there is the need for a camera — but not just any camera. The
camera does not have to have many of the features offered on today’s state-of­the-art equipment. For example, you don’t need auto focus capability or mirror
lock up. Here are the mandatory features a camera needs for celestial photog­raphy. First, a ‘B’ setting which allows for time exposures. This excludes
point and shoot cameras and limits the selection to 35mm SLR cameras.

Second, the ‘B’ or manual setting should not run off the battery. Many new
electronic cameras use the battery to keep the shutter open during time
exposures. Once the batteries are drained, usually after a few minutes, the
shutter closes, whether you have finished with the exposure or not. Look for a
camera that has a manual shutter when operating in the time exposure mode.
Olympus, Nikon, Minolta, Pentax, Canon and others have made such camera
bodies.

The camera should have interchangeable lenses so you can attach it to the
telescope and use a variety of lenses for piggyback photography. If you can’t
find a new camera, you can purchase a used camera body that is not 100­percent functional. The light meter does not have to be operational since you
will be determining the exposure length manually.

Use a cable release with a locking function to hold the shutter open while you
do other things. Mechanical and air releases are available at most camera
stores.

Celestial Photography • 47

Short Exposure Prime
Focus

Short exposure prime focus photography is the best way to begin recording celestial
objects. It is done with the camera attached to the telescope without an eyepiece or
camera lens in place. To attach your camera, you need the T-adapter and a T-Ring
for your specific camera (i.e., Minolta, Nikon, Pentax, etc.). The C150-HD and G-8N
focuser have built-in T-adapter and are ready to accept a 35mm camera body. The T­Ring replaces the 35mm SLR camera’s normal lens. Prime focus photography
allows you to capture the entire solar disk (if using the proper filter) as well as the
entire lunar disk. To attach your camera to your telescope:

1 Remove the eyepiece from the 1
2 Unthread the 1

1

/

" eyepiece holder from the focuser assembly. This will

4

1

/

" eyepiece holder.

4

expose the male thread of the built-in T-adapter.

3 Thread the T-ring onto the exposed T-adapter threads.
4 Mount your camera body onto the T-Ring the same as you would any other

lens.

With your camera attached to the telescope, you are ready for prime focus
photography. Start with an easy object like the Moon. Here’s how to do it:

1. Load your camera with film that has a moderate-to-fast speed (i.e., ISO
rating). Faster films are more desirable when the Moon is a crescent.
When the Moon is near full, and at its brightest, slower films are more
desirable. Here are some film recommendations:

• T-Max 100

• T-Max 400

• Any 100 to 400 ISO color slide film

• Fuji Super HG 400

2. Center the Moon in the field of your telescope.

3. Focus the telescope by turning the focus knob until the image is sharp.

4. Set the shutter speed to the appropriate setting (see table 6-1).

5. Trip the shutter using a cable release.

6. Advance the film and repeat the process.

Lunar Phase ISO 50 ISO 100 ISO 200 ISO 400
Crescent 1/ 2 1/ 4 1/ 8 1/15
Quarter 1/15 1/30 1/60 1/125
Full 1/30 1/60 1/125 1/250

Table 6-1

Above is a listing of recommended exposure times when photographing the Moon at the
prime focus of your Celestron Newtonian.

48 • Celestial Photography

The exposure times listed here should be used as a starting point. Always make
exposures that are longer and shorter than the recommended time. Also, try
bracketing your exposures, taking a few photos at each shutter speed. This will
ensure that you will get a good photo. If using black and white film, try a yellow
filter to reduce the light intensity and to increase contrast.

Keep accurate records of your exposures. This information is useful if you
want to repeat your results or if you want to submit some of your photos to
various astronomy magazines for possible publication!

Piggyback

The easiest way to enter the realm of deep-sky, long exposure astrophotography is
via the piggyback method. Piggyback photography is done with a camera and its
normal lens riding on top of the telescope. Through piggyback photography you
can capture entire constellations and record large scale nebulae that are too big for
prime focus photography. Because you are photographing with a low power lens
and guiding with a high power telescope, the margin for error is very large. Small
mistakes made while guiding the telescope will not show up on film. To attach the
camera to the telescope, use the piggyback adapter screw located on the top of the
tube mounting ring (see figure2-1). It will be neccessary to remove the finder
scope bracket before attaching the camera. In order to guide the exposure, you
will need an optional motor drive (#93518 or #93523).

As with any form of deep-sky photography, it should be done from a dark sky
observing site. Light pollution around major urban areas washes out the faint
light of deep-sky objects. You can still practice from less ideal skies.

1. Polar align the telescope (using one of the methods described earlier) and

start the motor drive.

2. Load your camera with slide film, ISO 100 or faster, or print film, ISO 400

or faster!

3. Set the f/ratio of your camera lens so that it is a half stop to one full stop

down from completely open.

4. Set the shutter speed to the “B” setting and focus the lens to the infinity

setting.

5. Locate the area of the sky that you want to photograph and move the

telescope so that it points in that direction.

6. Find a suitable guide star in the telescope eyepiece field of view. This is

relatively easy since you can search a wide area without affecting the area
covered by your camera lens. If you do not have an illuminated cross hair
eyepiece for guiding, simply defocus your guide star until it fills most of the
field of view. This makes it easy to detect any drift.

7. Release the shutter using a cable release.

8. Monitor your guide star for the duration of the exposure making the neccessary

corrections needed to keep the star centered.

Celestial Photography • 49

9. Close the camera’s shutter.

As for lenses, use good ones that produce sharp images near the edge of the
field. The lenses should have a resolving power of at least 40 lines per millime­ter. A good focal length range is 50 to 500mm for lenses designed for 35mm
cameras.

The exposure time depends on the film being used. However, five minutes is
usually a good starting point. With slower films, like 100 ISO, you can expose as
long as 45 minutes. With faster films, like 1600 ISO, you really shouldn’t expose
more than 5 to 10 minutes. When getting started, use fast films to record as much
detail in the shortest possible time. Here are proven recommendations:

• Ektar 1000 (color print)

• Konica 3200 (color print)

• Fujichrome 1600D (color slide)

• 3M 1000 (color slide)

• T-Max 3200 (black and white print)

• T-Max 400 (black and white print)

As you perfect your technique, try specialized films, that is films that are
designed or specially treated for celestial photography. Here are some popular
choices:

• Ektar 125 (color print)

• Fujichrome 100D (color slide)

• Tech Pan, gas hypered (black and white print)

As with all forms of photography, keep accurate records of your work. This
information can be used later if you want to reproduce certain results or if you
want to submit photos for possible publication.

Once you have mastered piggyback photography with wide angle and normal
lenses, try longer focal length lenses. The longer the focal length, the more
accurate your guiding must be. You can continue to increase the focal length
of the lens until you are ready for prime focus photography with your Celestron
telescope.

50 • Celestial Photography

TELESCOPE MAINTENANCE

After you have set up your telescope and started using it, there are a few things to
remember for future reference.

Care and Cleaning
of the Optics

Collimation

To minimize the need to clean your telescope, replace all lens covers once you
have finished using it. Since the front of the telescope tube is open ALWAYS
replace the front cover when the telescope is not in use. This will minimize the
amount of contaminants from entering the optical tube and minimize the number
of times your telescope needs to be cleaned.

The long tube of your Newtonian telescope acts as a dew shield to prevent moisture
from building up on the primary mirror. However, on extremely damp nights, the
tube may only slow the formation of dew on the primary mirror. If dew condenses
on the primary mirror it can be removed with a hair dryer or by pointing the tele­scope at the ground.

Occasionally, dust and/or moisture may build up on the primary mirror of your
telescope. Special care should be taken when cleaning any optical instrument so as
not to damage the optics. Internal adjustments and cleaning should be done only
by the Celestron repair department. If your telescope is in need of internal
cleaning, please call the Celestron repair department for specific information on
service.

Exact mirror alignment (i.e., collimation) of a fast f-number Newtonian reflector is
necessary in order to obtain the best optical image quality possible. Although your
telescope was fully collimated at the factory, you should check collimation to
ensure that rough handling has not altered the alignment of the mirrors.

To determine whether or not recollimation is necessary, the telescope should be
set up outside at night. It should be a still night and one in which you have let the
telescope sit outside for 30 to 45 minutes before attempting collimation. You
should also wait for a night with good seeing conditions and avoid looking over
anything that produces heat waves (i.e., roof tops, car hoods, etc.).

Pick a bright star and center it in the field of the telescope. Study the image of the
star while racking it in and out of focus using 30 to 60 power for every inch of
aperture. For your G-8N this equates to about 240 to 480 power and for the C150­HD is about 180 to 360 power.. If an unsymmetrical focus pattern is present, then it
may be possible to correct this by recollimating only the primary mirror. Simply
removing the ocular during the daytime and looking down the focus tube is NOT a
satisfactory way of determining collimation. Read the procedural instructions
through completely BEFORE attempting!

To star collimate, the telescope should be on either a motor driven (i.e., tracking)
equatorial mount that is approximately polar aligned or pointed at a stationary star
without the motor drive running. Polaris, the North Star, is the perfect collima­tion star for northern hemisphere observers since it appears motionless against the
background sky long enough to perform the collimation procedure. Polaris is the
last star in the handle of the Little Dipper (Ursa Minor) and its distance above the
northern horizon is always equal to your latitude angle.

Maintenance • 51

Prior to collimating the primary mirror holder, locate the three (3) screws on the end
plate at the end of the tube. Unthread the three screws and remove the plate from the
end of the tube. Under the end plate there are three (3) sets of two (2) screws. The
shorter Allen screws push the mirror holder which is held by the longer outer screws.
In order to make an adjustment, the outer screw is loosened while the shorter screw is
turned in or out. Then, the outer screw is tightened. Only one of the three (3) sets is
adjusted at a time. Normally motions on the order of 1/8 turn will make a difference,
with only about 1/2 to 3/4 turn being the maximum required.

Do NOT remove

or back out the holder screws more than one (1) to two (2) turns!

With Polaris or a bright star centered in the field of view, focus with your highest
power eyepiece (i.e., one with the shortest focal length). This includes eyepieces
in the 4mm to 6mm range. The star should be well centered to avoid confusing
collimation problems with coma, a problem common to all Newtonian telescopes
especially near the edge of the field. If you notice a flare in the star at one side
(same side) just as you go inside and outside of exact focus, then collimation will
help sharpen the image.

Take note of the direction of the flare. For example, if the flare is toward the 3
o’clock position in the field of view, then you must adjust the screw or combina­tion of collimation screws necessary to move the star TOWARD the direction of
the flaring. In this case you want to move the star with the adjusting screw to the
right, toward the 3 o’clock position in the eyepiece field of view. It may only be
necessary to adjust the screw to move the star from the center to about half way or
less toward the field’s edge (for higher power oculars). Prior to making any
adjustment, it is advisable to gently back off the pressure on the three (3) outer
screws to where they are snug, yet easily loosened without moving the telescope
unnecessarily.

Collimation adjustments are best made while viewing the star’s position in the field
of view while turning the adjustment screws. This way you can see exactly which
way the movement occurs. It may be helpful for two people working together,
while one views and instructs the other which screws are correctly turned and by
how much. Start by loosening the outer screws and advancing an inner screw to
see if the motion is correct. If not, undo what you did and try another set of
screws.

IMPORTANT: After making the first of each adjustment, it is necessary to reaim the telescope tube

to center the star again in the field of view. It can then be judged for symmetry by
going just inside and outside of exact focus and noting the star’s pattern. Improve­ment should be seen if the proper adjustments are made. Since three (3) sets of
screws are present, it may be necessary to move at least two (2) sets of screws to
achieve the necessary mirror movement. Do NOT over tighten the outer holding
screws!

Once in collimation, your telescope should not need additional collimation unless
the telescope has been bumped or jarred severely. In fact, most observers will find
the telescope’s collimation right out of the box to be satisfactory. Exact collimation
is only necessary for discriminating observers that require optimal imagery. Adjust­ing the secondary mirror is NOT needed unless the telescope has been dropped or
damaged. If it requires an adjustment, contact your local astronomy club for more
detailed instructions, consult a telescope users handbook, or call the Celestron
technical support department.

52 • Maintenance

OPTIONAL ACCESSORIES

The following is a partial list of optional accessories available for your Celestron
C150-HD and G-8N.

Barlow Lens - A Barlow lens is a negative lens that increases the focal length
of a telescope. Used with any eyepiece, it doubles the magnification of that
eyepiece. Celestron offers two Barlow lens in the 1-1/4" size for the C150-HD
and G-8N. The 2x Ultima Barlow (#93506) is a compact triplet design that is
fully multicoated for maximum light transmission and parfocal when used with
the Ultima eyepieces. Model #93507 is a compact achromatic Barlow lens that
is under three inches long and weighs only 4 oz. It works very well with all
Celestron eyepieces.

CD-ROM (93700) - Celestron and Software Bisque have joined together to
present this comprehensive CD-ROM called
It features a 10,000 object database, 75 color images, horizontal projection,
custom sky chart printing, zoom capability, Comet Hale-Bopp coordinates and
more! A fun, useful and educational product. PC format.

Dual Axis Drive System - #93523

This drive motor, with drive corrector capabilities, is designed for Celestron’s
CG-5 Equatorial telescope mount. It precisely controls the telescope’s
tracking speed during long, timed exposures of celestial objects, producing the
best possible image sharpness. Drive correctors are a must for those with
serious interest in astrophotography or CCD imaging.This precision, state-of­the-art DC motor drive operates on D-Cell batteries. The hand controller
module is very compact and fits easily in the palm of your hand. Motors for
both axes are included, along with brackets, clutches and hardware.

The Sky™ Level 1 - for Celestron.

Eyepieces - Like telescopes, eyepieces come in a variety of designs. Each
design has its own advantages and disadvantages. For the 1-1/4" barrel
diameter there are four different eyepiece designs available.

• Super Modified Achromatic (SMA) Eyepieces:
The SMA design is an improved version of the Kellner eyepiece. SMAs
are very good, economical, general purpose eyepieces that deliver a
wide apparent field, good color correction and an excellent image at the
center of the field of view. Celestron offers SMA eyepieces in the following
focal lengths: 6mm, 10mm, 12mm,17mm and 25mm.

• Plössl - Plössl eyepieces have a 4-element lens designed for low-to-high
power observing. The Plössls offer razor sharp views across the entire
field, even at the edges! In the 1-1/4" barrel diameter, they are available in
the following focal lengths: 6.3mm, 7.5mm, 10mm, 12.5mm, 17mm,
20mm, 26mm, 32mm and 40mm.

• Ultima - Ultima is not really a design, but a trade name for our 5-element,
wide field eyepieces. They are available in the following focal lengths:
5mm, 7.5mm, 12.5mm, 18mm, 24mm, 30mm, 35mm, and 42mm. These
eyepieces are all parfocal.

Optional Accessories • 53

• Lanthanum Eyepieces (LV Series) - Lanthanum is a unique rare earth
glass used in one of the field lenses of this new eyepiece. The Lantha­num glass reduces aberrations to a minimum. All are fully multicoated
and have an astounding 20mm of eye relief — perfect for eyeglass
wearers! They are available in the following focal lengths: 2.5mm, 4mm,
5mm, 6mm, 9mm, 10mm, 12mm, 15mm, 20mm and 25mm. Celestron
also offers the LV Zoom eyepiece (#3777) with a focal length of 8mm to
24mm. It offers an apparent field of 40o at 24mm and 60o at 8mm. Eye
relief ranges from 15mm to 19mm.

Eyepiece Filters - To enhance your visual observations of solar system
objects, Celestron offers a wide range of colored filters that thread into the 1-1/
4" oculars. Available individually are: #12 deep yellow, #21 orange, #25 red,
#58 green, #80A light blue, #96 neutral density - 25%T, #96 neutral density ­13%T, and polarizing. These and other filters are also sold in sets.

Finderscopes - Finderscopes are used to help you locate objects in the main
telescope. The larger the finder, the more you will see, making it easier to
locate objects. One option for finders is the Polaris 7x50 Finder (#93785-8P).
It comes with the finderscope, bracket and Polaris Setting Plate.

Another tool for finding objects in the sky is the Star Pointer (#51630). The
Star Pointer is different from a finderscope in that you can use both eyes when
pointing the telescope at an object. A partially reflective surface projects the
image of an LED illuminated pinpoint into the line of sight. Just align the
illuminated pinpoint with the object you are interested in and the object will be
in the main telescope.

Night Vision Flashlight - (#93588) - Celestron’s premium model for as-
tronomy, using two red LEDs to preserve night vision better than red filters or
other devices. Brightness is adjustable. Operates on a single 9 volt battery
(included).

Light Pollution Reduction (LPR) Filters (#94126A)- This 1

1

/

" filter is

4

designed to enhance your views of deep sky astronomical objects when viewed
from urban areas. LPR Filters selectively reduce the transmission of certain
wavelengths of light, specifically those produced by artificial lights. This
includes mercury and high and low pressure sodium vapor lights. In addition,
they also block unwanted natural light (sky glow) caused by neutral oxygen
emission in our atmosphere.

Micro Guide Eyepiece (#94171) - This multipurpose 12.5mm illuminated
reticle can be used for guiding deep-sky astrophotos, measuring position
angles, angular separations, and more. The laser etched reticle provides razor
sharp lines and the variable brightness illuminator is completely cordless.

Moon Filter (94119-A) - Celestron’s Moon Filter is an economical eyepiece
filter for reducing the brightness of the moon and improving contrast, so
greater detail can be observed on the lunar surface. The clear aperture is
21mm and the transmission is about 18%.

54 • Optional Accessories

Single Axis Motor Drive System - #93518

By adding the MDCG-5 Drive System to your mount, you add the capacity to

automatically

during long viewing or astrophotography sessions, when manual tracking can
become tiring. Furthermore, the Drive System will enhance high-power visual
observing. It attaches to the R.A. (east/west) drive axis of your CG-5 Mount
and will drive the telescope at the normal sidereal rate as well as allowing you
to guide at 2x and 4x sidereal. Power is supplied via a DC battery pack.

Planisphere (93720) - A simple and inexpensive tool for all levels of observers,
from naked eye viewers to users of highly sophisticated telescopes. The
Celestron Planisphere makes it easy to locate stars for observing and is a
great planet finder as well. A map of the night sky, oriented by month and day,
rotates within a depiction of the 24 hours of the day, to display exactly which
stars and planets will be visible at any given time. Ingeniously simple to use,
yet quite effective. Made of durable materials and coated for added
protection. Celestron Planispheres come in three different models, to match
the latitude from which you’re observing:

For 20

° to 40° of latitude #93720-30

For 30° to 50° of latitude #93720-40
For 40° to 60° of latitude #93720-50

Polarizing Filter Set (#93608) - The polarizing filter set limits the transmis­sion of light to a specific plane, thus increasing contrast between various
objects. This is used primarily for terrestrial, lunar and planetary observing.

track objects in the sky, a convenience you’ll be sure to enjoy

Polar Axis Finderscope (#94221) - This useful accessory speeds accurate

polar alignment by providing a means of visually aligning your German equato­rial mount with Polaris and true north. The finderscope has an eyepiece with
etched reticle for quick polar alignment.

Sky Maps (#93722) - Celestron Sky Maps are the ideal teaching guide for
learning the night sky. You wouldn’t set off on a road trip without a road map,
and you don’t need to try to navigate the night sky without a map either. Even
if you already know your way around the major constellations, these maps can
help you locate all kinds of fascinating objects.

T-Ring - The T-Ring couples your 35mm SLR camera body to the T-Adapter,
radial guider, or tele-extender. This accessory is mandatory if you want to do
photography through the telescope. Each camera make (i.e., Minolta, Nikon,
Pentax, etc.) has its own unique mount and therefore, its own T-Ring.
Celestron has 9 different models for 35mm cameras.

A full description of all Celestron accessories can be found in the
Celestron accessory catalog (#93685).

Optional Accessories • 55

THE MESSIER CATALOGTHE MESSIER CATALOG

THE MESSIER CATALOG

THE MESSIER CATALOGTHE MESSIER CATALOG

The Messier Catalog, compiled by Charles Messier, was the first extensive listing of star clusters and nebulae.
Messier’s primary observational purpose was to discover comets. He compiled this list so that others searching
for comets would not be confused by these objects. His list still remains popular today because all of these
objects are easily visible in amateur telescopes.

M#M#

M#

M#M#

M1 NGC 1952 Tau 5 34.5 22 01 8 .4 P. Neb. Crab Nebula
M2 NGC 7089 Aqr 21 33.5 -00 49 6 .5 Gl. Cl.
M3 NGC 5272 CVn 13 42.2 28 23 6 .4 Gl. Cl.
M4 NGC 6121 S co 16 23.6 -26 32 5 .9 Gl. Cl.
M5 NGC 5904 Se r 15 18.5 2 05 5.8 Gl. Cl.

M6 NGC 6405 S co 17 40.0 -32 13 4. 2 Op. Cl. Butterfly Cluster
M7 NGC 6475 S co 17 54.0 -34 49 3 .3 Op. Cl.
M8 NGC 6523 Sg r 18 03.7 -24 23 5.8 D. Neb. Lagoon Nebula
M9 NGC 6333 Oph 17 19.2 -18 31 7.9 Gl. Cl.
M10 NGC 6254 Oph 16 57.2 -4 06 6. 6 Gl. Cl.

M11 NGC 6705 S ct 18 51.1 -6 16 5.8 Op. Cl. Wild Duck Cluster
M12 NGC 6218 Oph 16 47.2 -1 57 6. 6 Gl. Cl.
M13 NGC 6205 Her 16 41.7 36 28 5 .9 Gl. Cl. Hercules Cluster
M14 NGC 6402 Oph 17 37.6 -3 15 7. 6 Gl. Cl.
M15 NGC 7078 P eg 21 30.0 12 10 6. 4 Gl. Cl.

M16 NGC 6611 Se r 18 18.9 -13 47 6. 0 D. Neb. Eagle Nebula
M17 NGC 6618 Sg r 18 20.8 -16 11 7.0 D. Neb. Omega Nebula
M18 NGC 6613 Sg r 18 19.9 -17 08 6. 9 Op. Cl.
M19 NGC 6273 Oph 17 02.6 -26 16 7.2 Gl. Cl.
M20 NGC 6514 Sg r 18 02.4 -23 02 8. 5 D. Neb. Trifid Nebula

NGC#NGC#

NGC#

NGC#NGC#

Const.Const.

Const.

Const.Const.

R.A.R.A.

R.A.

R.A.R.A.

H M SH M S

H M S

H M SH M S

DECDEC

DEC

DECDEC

° ‘° ‘

° ‘

° ‘° ‘

MagMag

Mag

MagMag

TypeType

Type

TypeType

Proper NameProper Name

Proper Name

Proper NameProper Name

M21 NGC 6531 Sg r 18 04.7 -22 30 5. 9 Op. Cl.
M22 NGC 6656 Sg r 18 36.4 -23 54 5.1 Gl. Cl.
M23 NGC 6494 Sg r 17 56.9 -19 01 5. 5 Op. Cl.
M24 NGC 6603 Sg r 18 16.4 -18 29 4. 5 Op. Cl.
M25 IC 4725 Sgr 18 31.7 -19 15 4.6 Op. Cl.

M26 NGC 6694 S ct 18 45.2 -9 24 8.0 Op. Cl.
M27 NGC 6853 Vul 19 59.6 22 43 8 .1 P. Neb. Dumbbell Nebula
M28 NGC 6626 Sg r 18 24.6 -24 52 6.9 Gl. Cl.
M29 NGC 6913 Cyg 20 23.0 38 32 6 .6 Op. Cl.
M30 NGC 7099 Cap 21 40.4 -23 11 7 .5 Gl. Cl.

M31 NGC 224 And 0 42.7 41 16 3. 4 Sp. Gx. Andromeda Galaxy
M32 NGC 221 And 0 42.7 40 52 8 .2 El. Gx.
M33 NGC 598 Tri 1 33.8 30 39 5 .7 Sp. Gx. Pinwheel Galaxy
M34 NGC 1039 Per 2 42.0 42 47 5 .2 Op. Cl.
M35 NGC 2168 Gem 6 08.8 24 20 5 .1 Op. Cl.

56 • The Messier Catalog

M#M#

M#

M#M#

M36 NGC 1960 Aur 5 36.3 34 08 6. 0 Op. Cl.
M37 NGC 2099 Aur 5 52.0 32 33 5. 6 Op. Cl.
M38 NGC 1912 Aur 5 28.7 35 50 6. 4 Op. Cl.
M39 NGC 7092 Cyg 21 32.3 48 26 4 .6 Op. Cl.
M40 UMa 12 22.2 58 05 8.0 dbl

M41 NGC 2287 CMa 6 47.0 -20 44 4 .5 Op. Cl.
M42 NGC 1976 Ori 5 35.3 -5 27 4.0 D. Neb. Great Orion Nebula
M43 NGC 1982 Ori 5 35.5 - 5 16 9 .0 D. Neb.
M44 NGC 2632 Cnc 8 40.0 19 59 3.1 Op. Cl. Beehive Cluster
M45 Tau 3 47.5 24 07 1.2 Op. Cl. Pleiades

M46 NGC 2437 Pup 7 41.8 -14 49 6 .1 Op. Cl.
M47 NGC 2422 Pup 7 36.6 -14 30 4 .4 Op. Cl.
M48 NGC 2548 Hya 8 13.8 -5 48 5.8 Op. Cl.
M49 NGC 4472 Vir 12 29.8 8 00 8.4 El. Gx.
M50 NGC 2323 Mon 7 03.0 -8 20 5 .9 Op. Cl.

M51 NGC 5194-5 CVn 13 29.9 47 12 8.1 Sp. Gx. Whirlpool Galaxy
M52 NGC 7654 Ca s 23 24.2 61 35 6 .9 Op. Gx.
M53 NGC 5024 Com 13 12.9 18 10 7.7 Gl. Cl.
M54 NGC 6715 Sgr 18 55.1 -30 29 7.7 Gl. Cl.
M55 NGC 6809 Sgr 19 40 .0 -30 58 7.0 Gl. Cl.

NGC#NGC#

NGC#

NGC#NGC#

Const.Const.

Const.

Const.Const.

R.A.R.A.

R.A.

R.A.R.A.

H M SH M S

H M S

H M SH M S

DECDEC

DEC

DECDEC

° ‘° ‘

° ‘

° ‘° ‘

MagMag

Mag

MagMag

TypeType

Type

TypeType

Proper NameProper Name

Proper Name

Proper NameProper Name

M56 NGC 6779 Lyr 19 16.6 30 11 8.2 Gl. Cl.
M57 NGC 6720 Lyr 18 53.6 33 02 9.0 P. Neb. Ring Nebula
M58 NGC 4579 Vir 12 37.7 11 49 9.8 Sp. Gx.
M59 NGC 4621 Vir 12 42.0 11 39 9.8 El. Gx.
M60 NGC 4649 Vir 12 43.7 11 33 8.8 El. Gx.

M61 NGC 4303 Vir 12 21.9 4 28 9 .7 Sp. Gx.
M62 NGC 6266 Oph 17 01.2 -30 07 6.6 Gl. Cl.
M63 NGC 5055 CVn 13 15.8 42 02 8 .6 Sp. Gx. Sunflower Galaxy
M64 NGC 4826 Com 12 56.7 21 41 8.5 Sp. Gx. Black Eye Galaxy
M65 NGC 3623 Leo 11 18.9 13 05 9 .3 Sp. Gx. Leo’s Triplet

M66 NGC 3627 Leo 11 20.3 12 59 9 .0 Sp. Gx. Leo’s Triplet
M67 NGC 2682 Cnc 8 50.3 11 49 6. 9 Op. Cl.
M68 NGC 4590 Hya 12 39.5 -26 45 8.2 Gl. Cl.
M69 NGC 6637 Sgr 18 31.4 -32 21 7.7 Gl. Cl.
M70 NGC 6681 Sgr 18 43.2 -32 18 8.1 Gl. Cl.

M71 NGC 6838 S ge 19 53.7 18 47 8.3 Gl. Cl.
M72 NGC 6981 Aqr 20 53.5 -12 32 9 .4 Gl. Cl.
M73 NGC 6994 Aqr 20 58.0 -12 38 a s t
M74 NGC 628 P s c 1 36.7 15 47 9.2 S
M75 NGC 6864 Sg r 20 06.1 -21 55 8.6 Gl Cl.

M76 NGC 650-1 P er 1 42.2 51 34 11.5 P. Neb. Cork Nebula
M77 NGC 1068 Cet 2 42.7 0 01 8.8 Sp. Gx.
M78 NGC 2068 Ori 5 46.7 0 03 8.0 D. Neb.
M79 NGC 1904 Lep 5 24.2 -24 33 8.0 Gl. Cl.
M80 NGC 6093 Sc o 16 17.0 -22 59 7.2 Gl. Cl.

The Messier Catalog • 57

M#M#

M#

M#M#

M81 NGC 3031 UMa 9 55.8 69 04 6 .8 Sp. Gx. Bodes Nebula
M82 NGC 3034 UMa 9 56.2 69 41 8.4 Ir. Gx.
M83 NGC 5236 Hya 13 37.7 -29 52 7.6 Sp. Gx.
M84 NGC 4374 Vir 12 25.1 12 53 9 .3 El. Gx.
M85 NGC 4382 Com 12 25.4 18 11 9.2 El. Gx.

M86 NGC 4406 Vir 12 26.2 12 57 9 .2 El. Gx.
M87 NGC 4486 Vir 12 30.8 12 24 8. 6 El. Gx. Virgo A
M88 NGC 4501 Com 12 32.0 14 25 9.5 Sp. Gx.
M89 NGC 4552 Vir 12 35.7 12 33 9 .8 El. Gx.
M90 NGC 4569 Vir 12 36.8 13 10 9 .5 Sp. Gx.

M91 NGC 4548 Com 12 35.4 14 30 10.2 Sp. Gx.
M92 NGC 6341 Her 17 17.1 43 08 6. 5 Gl. Cl.
M93 NGC 2447 Pup 7 44.6 -23 52 6 .2 Op. Cl.
M94 NGC 4736 CVn 12 50.9 41 07 8 .1 Sp. Gx.
M95 NGC 3351 Leo 10 44.0 11 42 9 .7 Sp. Gx.

M96 NGC 3368 Leo 10 46.8 11 49 9 .2 Sp. Gx.
M97 NGC 3587 UMa 11 14.9 55 01 11.2 P. Neb. Owl Nebula
M98 NGC 4192 Com 12 13.8 14 54 10.1 Sp. Gx.
M99 NGC 4254 Com 12 18.8 14 25 9.8 Sp. Gx. Pin Wheel Nebula
M100 NGC 4321 Com 12 22.9 15 49 9 .4 Sp. Gx.

NGC#NGC#

NGC#

NGC#NGC#

Const.Const.

Const.

Const.Const.

R.A.R.A.

R.A.

R.A.R.A.

H M SH M S

H M S

H M SH M S

DECDEC

DEC

DECDEC

° ‘° ‘

° ‘

° ‘° ‘

MagMag

Mag

MagMag

TypeType

Type

TypeType

Proper NameProper Name

Proper Name

Proper NameProper Name

M101 NGC 5457 UMa 14 03.2 54 21 7.7 Sp. Gx.
M102 NGC 5457 UMa 14 03.2 54 21 7.7 dup
M103 NGC 581 C as 1 33.1 60 42 7.4 Op. Cl.
M104 NGC 4594 Vir 12 40.0 -11 37 8.3 Sp. Gx. Sombrero Galaxy
M105 NGC 3379 Leo 10 47.9 12 35 9 .3 El. Gx..

M106 NGC 4258 CVn 12 19.0 47 18 8 .3 Sp. Gx.
M107 NGC 6171 Oph 16 32.5 -13 03 8.1 Gl. Cl.
M108 NGC 3556 UMa 11 11.6 55 40 10.0 Sp. Gx.
M109 NGC 3992 UMa 11 57.7 53 23 9.8 Sp. Gx.
M110 NGC 205 And 0 40.3 41 41 8 .0 El. Gx.

Object Abbreviations:

• Sp. Gx. ................Spiral Galaxy

• El. Gx. ................. Elliptical Galaxy

• Ir. Gx. ...................Irregular Galaxy

• Op. Cl. ................. Open Cluster

• Gl. Cl. .................. Globular Cluster

• D. Neb.................. Diffuse Nebula

• P. Neb.................. Planetary Nebula

NOTE:NOTE:

NOTE: Al l coordi nates fo r th e obj ects in the Messier catalog are listed in epoch 2000.00.

NOTE:NOTE:

58 • The Messier Catalog

LIST OF BRIGHT STARSLIST OF BRIGHT STARS

LIST OF BRIGHT STARS

LIST OF BRIGHT STARSLIST OF BRIGHT STARS

The following is a list of bright stars that can be used to align the R.A. setting circle. All coordinates are in
epoch 2000.0.

Epoch 2000.0Epoch 2000.0

Epoch 2000.0

Epoch 2000.0Epoch 2000.0

Star NameStar Name

Star Name

Star NameStar Name

Sirius CMa 06 45 09 -16 42 58 -1.47
Canopus Car 06 23 57 -52 41 44 -0.72
Arcturus Boo 14 15 40 +19 10 57 -0.72
Rigel Kent. Cen 14 39 37 -60 50 02 +0.01
Vega Lyr 18 36 56 +38 47 01 +0.04

Capella Aur 05 16 41 +45 59 53 +0.05
Rigel Ori 05 14 32 -08 12 06 +0.14
Procyon CMi 07 38 18 +05 13 30 +0.37
Betelgeuse Ori 05 55 10 +07 24 26 +0.41
Achernar Eri 01 37 43 -57 14 12 +0.60

Hadar Cen 14 03 49 -60 22 22 +0.63
Altair Aqi 19 50 47 +08 52 06 +0.77
Aldebaran Tau 04 35 55 +16 30 33 +0.86
Spica Vir 13 25 12 -11 09 41 +0.91
Antares S c o 16 29 24 -26 25 55 +0.92

ConstellationConstellation

Constellation

ConstellationConstellation

R.A.R.A.

R.A.

R.A.R.A.

H M SH M S

H M S

H M SH M S

DECDEC

DEC

DECDEC
° ‘ “° ‘ “

° ‘ “

° ‘ “° ‘ “

MagnitudeMagnitude

Magnitude

MagnitudeMagnitude

Fomalhaut PsA 22 57 39 -29 37 20 +1.15
Pollux Gem 07 45 19 +28 01 34 +1.16
Deneb Cyg 20 41 26 +45 16 49 +1.28
Beta Crucis Cru 12 47 43 -59 41 19 +1.28
Regulus Leo 10 08 22 +11 58 02 +1.36

List of Bright Stars • 59

FOR FURTHER READING

The following is a list of astronomy books that will further enhance your understanding of the night sky. The
books are broken down by classification for easy reference.

Astronomy Texts

Astronomy Now .................................................................................................... Pasachoff & Kutner

Cambridge Atlas Of Astronomy .......................................................................... Audouze & Israel

McGraw-Hill Encyclopedia Of Astronomy ......................................................... Parker

Astronomy-The Evolving Universe ....................................................................... Zeilik

Atlases

Atlas Of Deep Sky Splendors ............................................................................. Vehrenberg

Sky Atlas 2000.0 ..................................................................................................Tirion

Sky Catalog 2000.0 Vol 1 & 2 ............................................................................ Hirshfeld & Sinnott

Uranometria Vol. 1 & 2 ........................................................................................ Tirion, Rappaport, Lovi

Magnitude 6 Star Atlas ........................................................................................ Dickinson, Costanzo, Chaple

NGC 2000.0........................................................................................................... Sinnott

General Observational Astronomy

The Cambridge Astronomy Guide ...................................................................... Liller & Mayer

A Complete Manual Of Amateur Astronomy ..................................................... Sherrod

The Guide To Amateur Astronomy ..................................................................... Newton & Teece

Visual Observation

Observational Astronomy For Amateurs ...........................................................Sidgwick

Astronomical Calendar......................................................................................... Ottewell

Burnham’s Celestial Handbook Vols. 1, 2 & 3 ................................................. Burnham

The Planet Jupiter................................................................................................. Peek

Field Guide To The Stars & Planets .................................................................. Menzel & Pasachoff

Observe Comets ...................................................................................................Edberg & Levy

Astrophotography

Skyshooting ..........................................................................................................Mayall & Mayall

Astrophotography A Step-by-Step Approach.................................................... Little

Astrophotography For The Amateur ................................................................... Covington

Astrophotography .................................................................................................Gordon

Astrophotography II .............................................................................................. Martinez

A Manual Of Celestial Photography ................................................................... King

Manual Of Advanced Celestial Photography .....................................................Wallis & Provin

Colours Of The Stars ............................................................................................ Malin & Muirden

60 • Astronomy Books

CELESTRON ONE YEAR WARRANTY

A. Celestron warrants this telescope to be free from defects in materials and workmanship for one year. Celestron will repair or

replace such product or part thereof which, upon inspection by Celestron, is found to be defective in materials or workmanship.
As a condition to the obligation of Celestron to repair or replace such product, the product must be returned to Celestron
together with proof-of-purchase satisfactory to Celestron.

B. The Proper Return Authorization Number must be obtained from Celestron in advance of return. Call Celestron at (310) 328-

9560 to receive the number to be displayed on the outside of your shipping container.

All returns must be accompanied by a written statement setting forth the name, address, and daytime telephone number of the
owner, together with a brief description of any claimed defects. Parts or product for which replacement is made shall become
the property of Celestron.

The customer shall be responsible for all costs of transportation and insurance, both to and from the factory of
Celestron, and shall be required to prepay such costs.

Celestron shall use reasonable efforts to repair or replace any telescope covered by this warranty within thirty days of receipt. In
the event repair or replacement shall require more than thirty days, Celestron shall notify the customer accordingly. Celestron
reserves the right to replace any product which has been discontinued from its product line with a new product of comparable
value and function.

This warranty shall be void and of no force of effect in the event a covered product has been modified in design or
function, or subjected to abuse, misuse, mishandling or unauthorized repair. Further, product malfunction or
deterioration due to normal wear is not covered by this warranty.

CELESTRON DISCLAIMS ANY WARRANTIES, EXPRESS OR IMPLIED, WHETHER OF MERCHANTABILITY OF
FITNESS FOR A PARTICULAR USE, EXCEPT AS EXPRESSLY SET FORTH HEREIN.

THE SOLE OBLIGATION OF CELESTRON UNDER THIS LIMITED WARRANTY SHALL BE TO REPAIR OR REPLACE
THE COVERED PRODUCT, IN ACCORDANCE WITH THE TERMS SET FORTH HEREIN. CELESTRON EXPRESSLY
DISCLAIMS ANY LOST PROFITS, GENERAL, SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHICH MAY
RESULT FROM BREACH OF ANY WARRANTY, OR ARISING OUT OF THE USE OR INABILITY TO USE ANY
CELESTRON PRODUCT. ANY WARRANTIES WHICH ARE IMPLIED AND WHICH CANNOT BE DISCLAIMED
SHALL BE LIMITED IN DURATION TO A TERM OF ONE YEAR FROM THE DATE OF ORIGINAL RETAIL
PURCHASE.

Some states do not allow the exclusion or limitation of incidental or consequential damages or limitation on how long an
implied warranty lasts, so the above limitations and exclusions may not apply to you.

This warranty gives you specific legal rights, and you may also have other rights which vary from state to state.

Celestron reserves the right to modify or discontinue, without prior notice to you, any model or style telescope.

If warranty problems arise, or if you need assistance in using your telescope contact:

Celestron
Customer Service Department
2835 Columbia Street
Torrance, CA 90503

Tel. [phone]
Fax. [phone]
Monday-Friday 8AM-4PM PST

This warranty supersedes all other product warranties.

NOTE: This warranty is valid to U.S.A. and Canadian customers who have purchased this product from an Authorized
Celestron Dealer in the U.S.A. or Canada. Warranty outside the U.S.A. and Canada is valid only to customers who
purchased from a Celestron Distributor or Authorized Celestron Dealer in the specific country and please contact them for
any warranty service.

2835 Columbia Street
Torrance, CA 90503
Tel. [phone]
Fax [phone]
www.celestron.com

Copyright 2002 Celestron
All rights reserved.

(Products or instructions may change
without notice or obligation.)

Item # 31058-INST
08-02
Price $10.00