Celestron XLT User Manual

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INTRODUCTION .......................................................................................................................................................... 4

Warning...................................................................................................................................................... 4

ASSEMBLY ....................................................................................................................................................................8

Setting up the Tripod.................................................................................................................................. 8

Attaching the Equatorial Mount................................................................................................................. 9

Attaching the Center Leg Brace............................................................................................................... 10

Installing the Counterweight Bar.............................................................................................................. 10

Installing the Counterweights................................................................................................................... 11

Attaching the Slow Motion Knobs........................................................................................................... 11

Attaching the Telescope Tube to the Mount............................................................................................. 12

Installing the Finderscope......................................................................................................................... 13

Installing the Visual Back......................................................................................................................... 13

Installing the Star Diagonal...................................................................................................................... 14

Installing the Eyepieces............................................................................................................................ 14

Moving the Telescope Manually.............................................................................................................. 15

Balancing the Mount in R.A..................................................................................................................... 15

Balancing the Mount in DEC ................................................................................................................... 16

Adjusting the Mount................................................................................................................................. 16

Adjusting the Mount in Altitude............................................................................................................... 17

Adjusting the Mount in Azimuth.............................................................................................................. 17

TELESCOPE BASICS................................................................................................................................................. 18

Image Orientation..................................................................................................................................... 20

Focusing ................................................................................................................................................... 20

Aligning the Finderscope......................................................................................................................... 21

Calculating Magnification........................................................................................................................ 21

Determining Field of View....................................................................................................................... 22

General Observing Hints.......................................................................................................................... 22

ASTRONOMY BASICS............................................................................................................................................... 23

The Celestial Coordinate System ............................................................................................................. 23

Motion of the Stars................................................................................................................................... 24

Latitude Scale........................................................................................................................................... 25

Pointing at Polaris .................................................................................................................................... 25

Finding the North Celestial Pole .............................................................................................................. 26

Declination Drift Method of Polar Alignment.......................................................................................... 27

Aligning the R.A. Setting Circle .............................................................................................................. 28

Using the R.A. Vernier Scale................................................................................................................... 29

CELESTIAL OBSERVING......................................................................................................................................... 30

Observing the Moon................................................................................................................................. 30

Lunar Observing Hints............................................................................................................................. 30

Observing the Planets............................................................................................................................... 30

Observing the Sun .................................................................................................................................... 31

Solar Observing Hints.............................................................................................................................. 31

Observing Deep Sky Objects.................................................................................................................... 31

Seeing Conditions..................................................................................................................................... 31

Transparency............................................................................................................................................ 31

Sky Illumination....................................................................................................................................... 31

Seeing....................................................................................................................................................... 32

Using the Lens Cap Aperture Stop with Refractor Telescopes................................................................ 32

ASTROPHOTOGRAPHY........................................................................................................................................... 33

Piggyback Photography............................................................................................................................ 33

Short Exposure Prime Focus Photography for Refractors & Newtonians................................................ 34

Short Exposure Prime Focus Photography for Schmidt-Cassegrains....................................................... 34

Eyepiece Projection for a Schmidt-Cassegrain......................................................................................... 35

Long Exposure Prime Focus Photography............................................................................................... 36

Planetary and Lunar Photography with Special Imagers.......................................................................... 37

CCD Imaging for Deep Sky Objects........................................................................................................ 38

Terrestrial Photography............................................................................................................................ 38

Metering ................................................................................................................................................... 38

Reducing Vibration.................................................................................................................................. 38

TELESCOPE MAINTENANCE................................................................................................................................. 39

Care and Cleaning of the Optics............................................................................................................... 39

Collimation of Refractors......................................................................................................................... 39

Collimation of a Schmidt-Cassegrain....................................................................................................... 40

Collimation of a Newtonian..................................................................................................................... 42

OPTIONAL ACCESSORIES..................................................................................................................................... 46

APPENDIX A TECHNICAL SPECIFICATIONS ................................................................................................. 49

APPENDIX B - GLOSSARY OF TERMS.................................................................................................................. 50

SKY MAPS.................................................................................................................................................................... 53

CELESTRON TWO YEAR WARRANTY ................................................................................................................59

Congratulations on your purchase of an Omni XLT Series telescope. The Omni XLT Series of telescopes come in several different models --- 102mm refractor, 120mm refractor, 150mm Newtonian, 127mm Schmidt-Cassegrain. The Omni Series is made of the highest quality materials to ensure stability and durability. All this adds up to a telescope that gives you a lifetime of pleasure with a minimal amount of maintenance. Furthermore, your Celestron telescope is versatile — it will grow as your interest grows. This instruction manual covers all the different models of the Omni XLT telescopes. .

No matter at what level you are starting out, the Omni XLT Series telescopes will unfold for you and your friends all the wonders of the Universe.

Some of the many standard features of the Omni XLT include:

• Hand selected optical glass and hand figured optics resulting in superior images.

• Premium Celestron Starbright XLT optical coatings that provide maximum contrast and image sharpness.

• Heavy-duty equatorial mount with a rugged and very stable stainless steel tripod.

• Ball bearings in both axes of the mount ensure smooth performance.

• CD-ROM “The Sky” --- astronomy software which provides education about the sky and printable sky maps. Many other high performance features! The Omni XLT deluxe features combined with Celestron’s legendary optical systems give amateur astronomers the most

sophisticated and easy to use telescopes available on the market today. Take time to read through this manual before embarking on your journey through the Universe. It may take a few observing

sessions to become familiar with your telescope, so you should keep this manual handy until you have fully mastered your telescope’s operation. The manual gives detailed information regarding each step as well as needed reference material and helpful hints guaranteed to make your observing experience as simple and pleasurable as possible.

Your telescope is designed to give you years 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 equipment.

WWaarrnniinngg

 Never look directly at the sun with the naked eye or with a telescope (unless you have the

proper solar filter). Permanent and irreversible eye damage may result.

 Never use your telescope to project an image of the sun onto any surface. Internal heat build-up can damage the telescope

and any accessories attached to it.

 Never use an eyepiece solar filter or a Herschel wedge. Internal heat build-up inside the telescope can cause these devices to

crack or break, allowing unfiltered sunlight to pass through to the eye.

Never leave the telescope unsupervised, either when children are present or adults who may not be familiar with the correct operating procedures of your telescope

Figure 1-1 Omni XLT 102 Refractor

(Omni XLT 120 Refractor similar)

1. Optical Tube 7. 1.75" Steel Tripod

2. Tube Rings 8. Accessory Tray/ Leg Brace

3. Finderscope 9. Counterweights

4. Eyepiece 10. Counterweight Bar

5. Equatorial Mount 11. Dovetail Slide Bar

6. Latitude Adjustment Screw 12. Objective Lens Shade

8 9

Figure 1-2 Omni XLT 150 Newtonian

1. Finderscope 7. 1.75" Steel Tripod

2. Finderscope Bracket 8. Accessory Tray/ Leg Brace

3. Focuser 9. Counterweights

4. Eyepiece 10. Counterweight Bar

5. Tube Rings 11. Dovetail Slide Bar

6. Equatorial Mount 12. Optical Tube

1. Optical Tube 7. 1.75" Steel Tripod

2. Finderscope 8. Counterweights

3. Finderscope Bracket 9. Counterweight Bar

Figure 1-3 Omni XLT 127 Schmidt-Cassegrain

4. Equatorial Mount 10. Declination Setting Circle

5. Latitude Scale 11. Dovetail Slide Bar

6. Accessory Tray/ Leg Brace 12. Schmidt Corrector Lens

This section covers the assembly instructions for your Celestron Omni XLT telescope. The equatorial mount is exactly the same for all the Omni telescope models and the optical tubes have some differences which will be noted. Your Omni telescope should be set up indoor the first time so that it is easy to identify the various parts and familiarize yourself with the correct assembly procedure before attempting it outdoor.

Each Omni telescopes comes in two boxes. One box contains the tripod, tripod accessory tray/brace, equatorial mount, counterweight bar, two counterweights, r.a. knob, dec. knob, polar axis polar cap, and a Phillips head screwdriver. The second box contains the telescope optical tube assembly, finderscope and bracket, eyepiece, and other standard accessory items per the specific model that you have.

SSeettttiinngg uupp tthhee TTrriippood

Remove the tripod from the box that it is in (Figure 2-1). The Omni tripod comes with an all metal center leg brace / accessory tray to give rock solid support to the mount. The tripod comes fully assembled with a metal plate, called the tripod head, that holds the legs together at the top. In addition, there is a central rod that extends down from the tripod head that attaches the equatorial mount to the tripod. To set up the tripod:

1. Stand the tripod upright and pull the tripod legs apart until each leg is fully extended. The tripod will now stand by

itself (Figure 2-2). Once the tripod is set up, you can adjust the height at which it stands.

2. Loosen the lever (turn counterclockwise) on the leg clamp so that the tripod leg can be adjusted (Figure 2-3).

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

4. Tighten the levers (turn clockwise) on each leg clamp to hold the legs in place.

5. The standard height of the tripod is 33” and it can be extended at any height up to a maximum of 47”. Remember

that the tripod will be the most rigid and stable at the lowest height.

Figure 2-1 Figure 2-2 Figure 2-3

AAttttaacchhiinngg tthhee EEqquuaattoorriiaall MMoouunntt

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 Omni mount is a German equatorial mount that tripod head there is a metal alignment peg for aligning the mount. This side of the tripod will face north when setting up for an astronomical observing session. To attach the equatorial head:

1. Locate the azimuth adjustment screws on the equatorial mount (see Figure 2-4).

2. Retract the screws so they no longer extend into the azimuth housing 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. You can rotate the mount slightly

but the center position (where the front latitude adj ustment screw is directly over the “N” on the tripod.

ighten the azimuth adjustm

Then t ent screws.

5. Tighten the mounting knob (attached to the central rod) on th e underside of the tripod head to hold the

equatorial mount firmly in place.

Equatorial Mount

Azimuth Adjustment

Figure 2-4

Screws

attaches to the tripod head. On one side of the

Figure 2-5

Tripod Head

Alignment Peg

Mounting Knob

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Tripod

Mounting Knob

Central Rod

Accessory Tray

1. Remove the accessory tray knob an om the central rod.

2. Slide the acces

tripod legs.

. Thread the accessory tray knob onto the central rod and tighten.

Innssttaalllliinngg tthhee CCoouunntteerrwweeiigghhtt BBaarr

o properly balance the telescope, the mount comes with a counterweight bar and two counterweights. To install

T th

e counterweight bar:

. Remove the counterweight safety screw from the counterweight bar (at the opposite end of the threaded end).

. Thread the counterweight bar through the counterweight bar locking nut.

3. Locate the opening in the equatorial mount on the . Thread the counterweight bar into the opening until tight.

Once the bar is securely in place you are ready to attach the counterweights.

Exhibit 2-6

d washer fr

sory tray over the central rod so that each arm of the tray is pushing against the inside of the

n5. Tighten the counterweight bar lock

Counterweight Bar Locking t

Counterweight Screw

Safety Screw

Accessory Tray Knob

DEC axis.

ut fully for added support (see fig 2-7).

Locking

Counterweights

Counterweight

Bar

Figure 2-7

Since the fully assembled telescope can be quite heavy, position the to

wards north before the tube assembly and counterweights are attached. This will make the polar

lignment procedure much easier.

IInnssttaalllliinngg tthhee C

Each Omni mount comes with two counterweights (One weights lbs. and the other weights 4 lbs.) To install the

ounterweight(s):

1. rient the mount so that the counterweigh t bar points toward the ground.

. Loosen the locking screw on the side of the counterweights (it doesn’t matter which counterweight you attach first)

so that the threads do not protrude through the center hole of th

Slide the counterweight onto the shaft (see Figure 2-7).

Tighten the locking screw on the side of the weight to hold the counterweigh

4. t in place.

S t onto the shaft and tighten as in # 4.

5. lide the second counterweigh

6. eplace the counterweight safety screw.

Attttaacchhiinngg tthhee SSllooww MMoottiioonn KKnnoobbss

he Omni mount comes with two slow motion

T c

ontrol knobs that allows you to make fine pointing

djustments to

Declination.

Locate the two knobs (both are identical) and make

1. sure the screw on each knob does not protrude through the knob shaft opening. Use the supplied Phillips head screwdriver.

. Line up the flat area on the inne

R.A. slow motion knob with the flat area on the R.A. shaft (see Fig 2-8).

3. Slide the R.A. slow motion knob onto the R shaft. There are two R.A. shafts, one on either side of the mount. It makes no difference which shaft you use since both w c

onvenient. If, If If after a few observing sessions, you find the R.A. slow motion knob is more accessible from the other side, reinstall it on the opp .

4. Tighten the screw on the R.A. knob to hold it securely in place.

the telescope in both R.A. and

To install the knobs:

Coouunntteerrwweeiigghhttss

e counterweight.

r portion of the

.A.

ork the same. Use whichever one you find more

mount so that the polar axis is pointing

Figure 2-8

osite side

5. 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 m tw

o shafts to choose from. Use the shaft that is pointing toward the ground. This makes it easy to reach while

oking through the telescope, something which is quite important wh en you are observing but again if it is more

convenient for you to use, then reinstall the knob that best

. Put the polar axis cap over the polar axis. It is held into place by a tension fit.

AAttttaacchhiinngg tthhee TTeelleessccooppee TTuub

he telescope optical tube attaches to the mount via a dovetail slide bar mounting bracket. For the refractors and the

T Newtonian, the mounting bracket is the long bracket Cassegrain the mounting bracket is attached along the b

tube, make sure that the declination and right ascen

the mount does not move su

emove the protective paper covering the optical tu

1 R be. You will have to remove the tube rings on the refractors

Newtonian before removing

and the paper.

2 Loosen the mounting knob and the mounting safety scre protrude into the mounting platform

ddenly while attaching the telescope optical tube. To mount the telescope tube:

ount, just below the telescope mounting platform. Once again, you have

suits your needs.

bee ttoo

tthhee MMoouunntt

which is attached to the tube rings. For the Schmidt-

ottom of the telescope tube. Before you attach the optical

sion clutch knobs (clamps) are tight. This will ensure that

w on the side of the mount platform so they do not

3. Slide the dovetail mounting bracket into the recess on the top of the mounting platform (see figure 2-9).

5 ighten the mounting knob on the Omni mounting

latform to hold the telescope in place.

Hand tighten the mounting platform safety screw u

ntil the tip touches the side of the mounting bracket.

OTE: Never loosen any of the knobs on the

lescope tube or mount other than the R.A. and

DEC knobs.

Newtonian and Schmidt-Cassegrain attach s

Figure 2-9 Refractor Optical Tube is shown. The

imilarly.

IInnssttaalllliinngg tthhee FFiinnddeerrssccooppe

To install the finderscope onto the telescope you must fi then attach it to the telescope. Toward the rear of the t fro

nt of the telescope tube (Newtonian), there is a small bracket with a set screw in it. This is where the

nderscope bracket will be mounted. To install the find

Loosen the finderscope adjus

1. tment screws so they don’t protrude into the bracket. Then slide the rubber

O-ring over the eyepiece end of the finder the slot (groove) in the finderscope.

2. Insert the eyepiece end of the findersc

narrow part of the bracket until the O-ring between the finder and the inside of the brac stops, then pull outward on the spring loaded adjustment screw and continue inserting the finderscope until it is approximately centered in the bracket.

3. Tighten the two adjustment screws until they make contact

with the finderscope body.

4. Locate the mounting bra

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

so it does not protrude in the bracket.

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

7. The finderscope bracket ill slide in from the back. The ted so that the

objective lens is toward e front (open) end of the telescope.

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

cket near the front (open) end of the telescope.

w finderscope should be orien

rst mount the finderscope through the finder bracket and

elescope tube (on refractors and Schmidt-Cassegrain) and

erscope:

scope (smallest diameter side) and roll it 2/3 of the way up into

ope through the

presses tightly

ket. Once it

Figure 2-10

or information on aligning your finderscope, see Telescope Basics section of this manual.

IInnssttaalllliinngg tthhee VViissuuaall BBaacck

Only applicable to the Schmidt-Cassegrain, the visual back is the accessory that allows you to attach all v the telescope. The Omni Schmidt-Cassegrain normally comes wi fo

llow these instructions for attaching it:

Remove the cover on the rear cell and then place the knurled slip ring on the visual back over the threads on

1. the rear ll (Fig 2-11).

Hold the visual back with the set screw in a convenient po

2. sitio til

t ht. Once this is done, you are ready to attach other accessories

ig hmidt-

assegrain), eyepieces, etc. If you want to remove the visual bac

C k, rotate the slip ring counterclockwise until it is

ee of the rear cell.

isual accessories to

th the visual back installed. If in case it is not installed,

n and rotate the knurled slip ring clockwise un

, such as diagonals (for refractors and the Sc

Innssttalllliinngg tthhee SSttaarr DDiiaaggoonnaall

TCar diagonal is a prism that diverts the light at a right angle to the light path of re

he st fractors and Schmidt-

rai telescopes. This allows you to observe in positions that

asseg n

ysically more comfortable than if you looked straight through.

are ph T

o attach t Schmidt-

assegrain:

he star diagonal onto the optical tube of a

Tu he set screw on the visual back until its tip no longer extends

1. rn t e., bstructs) the inner diameter of the visual back.

into (i. o

2. Slide t

3. ighten the set screw on the visual back to hold the star diagonal in

1. oosen the set screw on the eyepiece adapter so that

he chrome portion of the star diagonal into the visual back.

T place.

you wish to change the orientation of the star diagonal, loosen the set screw on the visual back until the star diagonal to the desired position and tighten t

Refractors – To use the star diagonal on refractor telescopes, it is inserted into the 1 ¼” eyepiece adapter.

Innssttaalllliinngg

The eyep Without o

f refractors and or into the visual

ack on the Schmidt-Cassegrain To attach an ocular:

L it does not obstruct the inner diameter of the ba

Slide the chrome portion of the eyepiece into the focuser.

Tighten the set screw to hold the eyepiece in place.

To remove th fo

cuser and slide the eyepiece out. You can replace

it with another ocular.

Many times it will be more comfortable to use a star diagonal on refractors and Schmidt-Cassegrain for most areas of the sky. an eyepiece into the star diagonal:

tthhee EEyyeeppiieeccees

iece, or ocular as it is also called, is an optical element that magnifies the image focused by the telescope.

the eyepiece it would be impossible to use the telescope visually. The eyepiece fits directly into the focuser

the Newtonian

e eyepiece, loosen the set screw on the

A. Loosen the set screw on the star diagonal until the tip no longer extends

into the inner diameter of the eyepiece end of the diagonal.

B. Slide the chrome portion of the eyepiece into the star C. Tighten the set screw on the star diagonal to hold the eyepiece i D. To remove the eyepiece, loosen the se

Slide the eyepiece out. You can replace it with other optional eyepieces.

diagonal rotates freely. Rotate the

he set screw.

rrel.

Focuser Knob

t screw on the star diagonal and

Star Diagonal

Visual Bac

Figure 2-11

Focuser Tension Screw

the Figure 2-12

To install

diagonal.

n place.

Eyepiece

1 ¼" Eyepiece Adapter

2" Focuser Barrel

T-Adapter

The refracting telescopes can use eyepieces and diagonals of a 2” barrel diameter. To use a 2” barrel eyepiece, the 1 ¼

” eyepiece adapter must first be removed. To do this, simply loosen the two chrome thumbscrews located around

e focuser barrel (see figure 2-12) and remove the 1 ¼” adapter. Once removed, a 2” eyepiece or accessory can be

inserted directly into the focuser barrel an

Eyepieces are commonly referred to by focal length and barrel diameter. The focal length of each eyepiece is printed on the eyepiece barrel. The longer the focal length (i.e., the larger the number) the lower the eyepiece magnification (i.e., power) and the shorter the focal le magnification. Generally, you will use low-to-modera determine power, see the section on “Calculating Mag

MMoovviinngg tthhee TTeelleessccooppee MMaannuuaalllly

In order to properly balance your telescope, you w the sky to and move the telescope in the desired direction.

Both the R.A. and DEC axis have lock levers to clutc the telescope, rotate the lock levers counterclockwise

Baallaanncciinngg tthhee MMoouunntt iinn RR..AA..

To e nced around the polar axis. In addi accurate tracking if using an optional motor drive. To balance the mount:

1. Release the R.A unt (make sure that the mounting bracket sc on the opposite side of the mount (see figure 2-12

2. Release the tele

3. Loosen the counterweight lock ing screw on the counterweight.

Move the counterweights to a point where they balance the telescope (i.e., it remains stationary when the R.A.

4. clamp is released).

Tighten the locking screw to hold the counterweights in place.

hese 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.

observe different objects. To make rough adjustments, lo osen the R.A. and DEC clutch knobs slightly

liminate undue stress on the mount, the telescope should be properly bala

tion, proper balancing is crucial for

. Clamp (see figure 2-13) and position the telescope off to one side of the mo

rew is tight). The counterweight bar will extend horizontally

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

DEC Clamp

d secured with the two thumb screws.

ngth (i.e., the smaller the number) the higher the

e power when viewing. For more information on how to

nification.”

ill need to move your telescope manually at various portions of

h down each axis of the telescope. To loosen the clutches on .

Figure 2-13

R.A. Clamp

BBaallaanncciinngg tthhee MMoouunntt iinn DDEEC

The telescope should also be balanced on the declination axis to prevent any sudden motions when the DEC clamp (Fig 2-13) is released. To balance the telescope in DEC:

. amp and rotate the telescope so that it is on one side of the mount (i.e., as described in the

Release the R.A. cl 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 2-15).

. Release the tube — GRADUALLY — to see which way it rotates around the declination axis. DO NOT LET GO

OF THE TELESCOPE TUBE COMPLETELY!

Loosen the screws that hold the telescope tube inside the mounting rings and slide the telescope either forwards or

5. backwards until it remains stationary when the DEC clamp is released.

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

Figure 2-14

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 b

Addjjuussttiinngg

In order for a motor drive to track accurately, the telescope’s axis of rotation must be parallel to the Earth’s axis o rotation, a process known as polar alignment. Polar alignment is achie DEC, but by adjusting the mount vertically, which is called altitud section simply covers the correct movement of the telescope durin of polar alignment, that is making the telescope’s axis of rotation parallel to the Earth’s, is described later in this m

anual in the section on “Polar Alignment.”

tthhee MMoouunnt

e done for the specific area at which the telescope is pointing.

ved NOT by moving the telescope in R.A. or e, and horizontally, which is called azimuth. This g the polar alignment process. The actual process

Figure 2-15

Rear Latitude Adjustment Screw

AAddjjuussttiinngg tthhee MMoouunntt iinn AAllttiittuuddee

• To increase the latitude of the polar axis, tighten the rear latitude adjustment screw and loosen the front screw (if necessary).

• To decrease the latitude of the polar axis, tighten the front (under the counterweight bar) latitude adjustment screw and loosen the rear screw (if necessary).

The latitude adjustment on the Omni mount has a range from approximately 20° going up to 60°.

It is best to always make final adjustments in altitude by moving the mount against gravity (i.e. using the rear latitude adjustment screw to raise the mount). To do this you should loosen both latitude adjustment screws and manually push the front of the mount down as far as it will go. Then tighten the rear adjustment screw to raise the mount to the desired latitude.

FrAdont Latitude

justment Screw

AzScimuth Adjustment

rew

Figure 2-16

AAddjjuussttiinngg tthhee MMoouunntt iinn AAzziimmuutth

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 knobs located on either side of the azimuth housing (see Fig 2-14). While standing behind the telescope, the knobs are on the front of the mount.

urning the right adjustment knob clockwise moves the mount toward the right. • T

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 sc o the tripod may have to be loosened slightly.

eep in mind that adjusting the mount is done during the polar alignment process only. Once polar aligned, the

K m

ount must NOT be moved. Pointing the telescope is done by moving the mount in right ascension and declination,

as described earlier in this manual.

rew that holds the equatorial mount t

A telescope is an instrument that collects and focuses light. The nature of the optical design determines how the light is focused.

ome tele opes, known as re telescopes, known as reflectors (Newtonians), use mirrors. Then, the

S sc fractors, use lenses. Other

chmidt- ssegrai elescop ses. Each optical design is briefly discussed below:

D in li . The refractor uses a l designs used single element lenses. However, the single len

w same point. Most two-element lenses, usually made of crown and flint glasses, are corrected for red and green light. Blue lig may still be focused at a slightly different point.

Ca n t e uses both mirrors and len

evelope in the early 1600s, is the oldest telescope design. It derives its name from the method it uses to focus

d the refractor

coming ght rays ens to bend or refra

ainbow, a phenomenon known as chromatic aberration. Tor

as introduced. Each element has a different index of refraction allowing two different wavelengths of light to be focused at the

ct incoming light rays, hence the name (see Figure 4-1). Early s acts like a prism and breaks light down into the colors of the get around this problem, a two-element lens, known as an achromat,

New

tonian reflector uses a single concave mirror as its primary. Light enters the tube traveling to the mirror at

e back end. There light is bent forward in the tube to a single point, its focal point. Since putting your head in

th front of the telescope to look at the image with an eyepiece would keep the reflector from working, a flat mirror called a diagonal intercepts the light and points it out the side of the tube at right angles to the tube. The eyepiece p

laced there for easy viewing.

Newtonian Reflector telescopes replace heavy lenses with mirrors to collect and focus the light, providing much more light-gathering power for the dollar. Because the light path is intercepted and reflected out to the side, yo have focal lengths up to 1000mm and still enjoy a telescope that is relatively compact and portable. A Newtonian Reflector telescope offers such impressive light-gathering characteristics you can take a serious interest in deep space astronomy even on a modest budget. Newtonian Reflector telescopes do require more care and maintenance because the primary mirror is exposed to air te

lescope’s popularity with those who want an economical telescope that can still resolve faint, distant objects.

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