31056
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
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▲ TELESCOPE MAINTENANCE......................................................................................................................... 51
▲▲
Care and Cleaning of the Optics................................................................................................................... 51
Collimation ................................................................................................................................................... 51
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▲ OPTIONAL ACCESSORIES .............................................................................................................................. 53
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▲▲
▲ THE MESSIER CATALOG................................................................................................................................ 56
▲▲
▲▲
▲ LIST OF BRIGHT STARS.................................................................................................................................. 59
▲▲
▲▲
▲ FOR FURTHER READING ................................................................................................................................ 60
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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
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