Celestron G-9.25 User manual

The G-9

1/4

Model #11037

INSTRUCTION MANUAL

Table of Contents • i

TT

TABLE OF CONTENTSABLE OF CONTENTS

ABLE OF CONTENTSABLE OF CONTENTS

ABLE OF CONTENTS

▲▲

▲INTRODUCTIONINTRODUCTION

INTRODUCTIONINTRODUCTION

INTRODUCTION ..........................................................................................................................................................................................................................................................

..........................................................................................................................................................................................................................................................

............................................................................................................................. 11

11

1

A Word of Caution .......................................................................................................................... 2

The Schmidt-Cassegrain Optical System ...........................................................................................2

▲▲

▲ASSEMBLING YOURASSEMBLING YOUR

ASSEMBLING YOURASSEMBLING YOUR

ASSEMBLING YOUR G-9G-9

G-9G-9

G-9

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TheThe

The G-9G-9

G-9G-9

G-9

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.......................................................................................................................................................................................................... 55

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Assembling the CG-5 EquatorialMount.............................................................. 6Assembling the CG-5 EquatorialMount.............................................................. 6

Assembling the CG-5 EquatorialMount.............................................................. 6

Setting Up the Tripod ......................................................................................................... 6

Adjusting the Tripod Height ................................................................................................ 6

Attaching the Accessory Tray ........................................................................................... 7

Attaching the Equatorial Mount ......................................................................................... 8

Attaching the R.A. Slow Motion Knob ................................................................... 9

Attaching the Declination Slow Motion Knob........................................................10

Attaching the Counterweight Bar and Counterweights ..........................................11

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

Removing the Lens Cap ....................................................................................................13

Balancing the Telescope in R.A. .......................................................................................14

Balancing the Telescope in DEC ...................................................................................... 14

Adjusting the Mount in Altitude .........................................................................................15

Adjusting the Mount in Azimuth ........................................................................................15

Disassembling and Transporting Your G-91/4......................................................................................................... 16

Storing Your G-9 1/4................................................................................................................................................................... 16

▲▲

▲TELESCOPE BASICSTELESCOPE BASICS

TELESCOPE BASICSTELESCOPE BASICS

TELESCOPE BASICS ..........................................................................................................................................................................................................................................

..........................................................................................................................................................................................................................................

..................................................................................................................... 1717

1717

17

Attaching the Accessories ...............................................................................................................17

The Visual Back ................................................................................................................17

The Star Diagonal .............................................................................................................17

The Eyepiece ....................................................................................................................18

Image Orientation .......................................................................................................................... 19

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

Aligning the Finder ........................................................................................................................21

Your First Look ............................................................................................................................. 22

Daytime Observing ........................................................................................................... 22

Nighttime Observing .........................................................................................................23

Calculating Magnification ...............................................................................................................24

Determining Field of View .............................................................................................................24

General Observing Hints ................................................................................................................25

General Photography Hints .............................................................................................................25

▲ ▲

▲ ASTRONOMY BASICSASTRONOMY BASICS

ASTRONOMY BASICSASTRONOMY BASICS

ASTRONOMY BASICS ......................................................................................................................................................................................................................................

......................................................................................................................................................................................................................................

................................................................................................................... 2626

2626

26

The Celestial Coordinate System ..................................................................................................... 27

Motion of the Stars .........................................................................................................................28

Polar Alignment ............................................................................................................................. 28

Finding the Pole ............................................................................................................................. 29

Latitude Scales ..................................................................................................................30

Pointing at Polaris .............................................................................................................31

Declination Drift ..............................................................................................................32

Polar Alignment Finders .................................................................................................... 33

Aligning the R.A. Setting Circle .........................................................................................33

ii • Table of Contents

▲ ▲

▲ CELESTIAL OBSERVINGCELESTIAL OBSERVING

CELESTIAL OBSERVINGCELESTIAL OBSERVING

CELESTIAL OBSERVING ......................................................................................................................................................................................................................

......................................................................................................................................................................................................................

........................................................................................................... 3434

3434

34

Observing the Moon ....................................................................................................................... 34

Observing the Planets .....................................................................................................................34

Observing the Sun .......................................................................................................................... 35

Observing Deep-Sky Objects ........................................................................................................... 36

Using the Setting Circles ....................................................................................................36

Star Hopping .....................................................................................................................37

Viewing Conditions ........................................................................................................................39

Transparency ....................................................................................................................39

Sky Illumination ...............................................................................................................39

Seeing ...............................................................................................................................39

▲ ▲

▲ CELESTIAL PHOTOGRAPHYCELESTIAL PHOTOGRAPHY

CELESTIAL PHOTOGRAPHYCELESTIAL PHOTOGRAPHY

CELESTIAL PHOTOGRAPHY ........................................................................................................................................................................................................

........................................................................................................................................................................................................

.................................................................................................... 4141

4141

41

Short Exposure Prime Focus ........................................................................................................... 42

Piggyback ...................................................................................................................................... 44

Eyepiece Projection ........................................................................................................................46

Long Exposure Prime Focus ........................................................................................................... 48

▲▲

▲TELESCOPE MAINTENANCETELESCOPE MAINTENANCE

TELESCOPE MAINTENANCETELESCOPE MAINTENANCE

TELESCOPE MAINTENANCE........................................................................................................................................................................................................

........................................................................................................................................................................................................

.................................................................................................... 5050

5050

50

Care and Cleaning of the Optics .......................................................................................................50

Collimation ................................................................................................................................... 50

Technical Specifications ................................................................................................................. 52

▲ ▲

▲ OPTIONAL ACCESSORIESOPTIONAL ACCESSORIES

OPTIONAL ACCESSORIESOPTIONAL ACCESSORIES

OPTIONAL ACCESSORIES ....................................................................................................................................................................................................................

....................................................................................................................................................................................................................

.......................................................................................................... 5353

5353

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▲THE MESSIER CATALOGTHE MESSIER CATALOG

THE MESSIER CATALOGTHE MESSIER CATALOG

THE MESSIER CATALOG ........................................................................................................................................................................................................................

........................................................................................................................................................................................................................

............................................................................................................ 5757

5757

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▲▲

▲LIST OF BRIGHT STARSLIST OF BRIGHT STARS

LIST OF BRIGHT STARSLIST OF BRIGHT STARS

LIST OF BRIGHT STARS ............................................................................................................................................................................................................................

............................................................................................................................................................................................................................

.............................................................................................................. 6060

6060

60

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▲FOR FURTHER READINGFOR FURTHER READING

FOR FURTHER READINGFOR FURTHER READING

FOR FURTHER READING ......................................................................................................................................................................................................................

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Introduction • 1

INTRODUCTIONINTRODUCTION

INTRODUCTION

Welcome to the Celestron world of amateur astronomy! For more than a quarter

of a century, Celestron has provided amateur astronomers with the tools needed to

explore the universe. The Celestron G-9 1/4continues in this proud tradition

combining large aperture optics with ease of use and portability. With a mirror

diameter of 9.25 inches, your Celestron has a light gathering power of 1,126 times

that of the unaided human eye. Yet despite its large aperture, the Celestron G-91/4

optical system is extremely compact and portable because it utilizes the Schmidt-

Cassegrain design. This means you can take your Celestron G-91/4to the moun-

tains or desert or wherever you observe.

The Celestron G-91/4is 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. And, your Celestron G-91/4is versatile -

it grows as your interest in astronomy grows.

Your Celestron G-91/4is not limited to astronomical viewing alone. It can also be

used for terrestrial viewing to study the world around you. All you need to do is

take the time to familiarize yourself with your Celestron telescope and its opera-

tion.

Read the assembly instructions through completely before you attempt to set up

your Celestron G-9 1/4telescope. Then, once you’ve set up your Celestron G-9 1/4

you should 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 Celestron G-91/4you should keep this manual handy until you

have fully mastered your telescope’s operation. After that, save the manual for

future reference.

2 • Introduction

Your G-91/4telescope is designed to give you hours of fun and rewarding observa-

tions. However, there are a few things to consider before using your telescope that

will ensure your safety and protect your equipment.

WARNING !WARNING !

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

NEVER LOOK DIRECTLY AT THE SUN WITH THE NAKEDNEVER LOOK DIRECTLY AT THE SUN WITH THE NAKED

NEVER LOOK DIRECTLY AT THE SUN WITH THE NAKED

EYE OR WITH A TELESCOPE. PERMANENT AND IRRE-EYE OR WITH A TELESCOPE. PERMANENT AND IRRE-

EYE OR WITH A TELESCOPE. PERMANENT AND IRRE-

VERSIBLE EYE DAMAGE MAY RESULT.VERSIBLE EYE DAMAGE MAY RESULT.

VERSIBLE EYE DAMAGE MAY RESULT.

NEVER USE YOUR TELESCOPE TO PROJECT AN IMAGE OFNEVER USE YOUR TELESCOPE TO PROJECT AN IMAGE OF

NEVER USE YOUR TELESCOPE TO PROJECT AN IMAGE OF

THE SUN ONTO ANY SURFACE. INTERNAL HEAT BUILD-THE SUN ONTO ANY SURFACE. INTERNAL HEAT BUILD-

THE SUN ONTO ANY SURFACE. INTERNAL HEAT BUILD-

UP CAN DAMAGE THE TELESCOPE AND/OR ANY ACCES-UP CAN DAMAGE THE TELESCOPE AND/OR ANY ACCES-

UP CAN DAMAGE THE TELESCOPE AND/OR ANY ACCES-

SORIES ATTACHED TO IT.SORIES ATTACHED TO IT.

SORIES ATTACHED TO IT.

NEVER USE AN EYEPIECE SOLAR FILTER OR A HERSCHELNEVER USE AN EYEPIECE SOLAR FILTER OR A HERSCHEL

NEVER USE AN EYEPIECE SOLAR FILTER OR A HERSCHEL

WEDGE. INTERNAL HEAT BUILD-UP INSIDE THE TELE-WEDGE. INTERNAL HEAT BUILD-UP INSIDE THE TELE-

WEDGE. INTERNAL HEAT BUILD-UP INSIDE THE TELE-

SCOPE CAN CAUSE THESE DEVICES TO CRACK OR BREAK,SCOPE CAN CAUSE THESE DEVICES TO CRACK OR BREAK,

SCOPE CAN CAUSE THESE DEVICES TO CRACK OR BREAK,

ALLOWING UNFILTERED SUNLIGHT TO PASS THROUGHALLOWING UNFILTERED SUNLIGHT TO PASS THROUGH

ALLOWING UNFILTERED SUNLIGHT TO PASS THROUGH

TO THE EYE.TO THE EYE.

TO THE EYE.

NEVER LEAVE THE TELESCOPE UNSUPERVISED, EITHERNEVER LEAVE THE TELESCOPE UNSUPERVISED, EITHER

NEVER LEAVE THE TELESCOPE UNSUPERVISED, EITHER

WHEN CHILDREN ARE PRESENT OR ADULTS WHO MAYWHEN CHILDREN ARE PRESENT OR ADULTS WHO MAY

WHEN CHILDREN ARE PRESENT OR ADULTS WHO MAY

NOT BE FAMILIAR WITH THE CORRECT OPERATINGNOT BE FAMILIAR WITH THE CORRECT OPERATING

NOT BE FAMILIAR WITH THE CORRECT OPERATING

PROCEDURES OF YOUR TELESCOPE.PROCEDURES OF YOUR TELESCOPE.

PROCEDURES OF YOUR TELESCOPE.

NEVER POINT YOUR TELESCOPE AT THE SUN UNLESSNEVER POINT YOUR TELESCOPE AT THE SUN UNLESS

NEVER POINT YOUR TELESCOPE AT THE SUN UNLESS

YOU HAVE THE PROPER SOLAR FILTER. WHEN USINGYOU HAVE THE PROPER SOLAR FILTER. WHEN USING

YOU HAVE THE PROPER SOLAR FILTER. WHEN USING

YOUR TELESCOPE WITH THE CORRECT SOLAR FILTER,YOUR TELESCOPE WITH THE CORRECT SOLAR FILTER,

YOUR TELESCOPE WITH THE CORRECT SOLAR FILTER,

ALWAYS COVER THE FINDER. ALTHOUGH SMALL INALWAYS COVER THE FINDER. ALTHOUGH SMALL IN

ALWAYS COVER THE FINDER. ALTHOUGH SMALL IN

APERTURE, THIS INSTRUMENT HAS ENOUGH LIGHTAPERTURE, THIS INSTRUMENT HAS ENOUGH LIGHT

APERTURE, THIS INSTRUMENT HAS ENOUGH LIGHT

GATHERING POWER TO CAUSE PERMANENT AND IRRE-GATHERING POWER TO CAUSE PERMANENT AND IRRE-

GATHERING POWER TO CAUSE PERMANENT AND IRRE-

VERSIBLE EYE DAMAGE. IN ADDITION, THE IMAGEVERSIBLE EYE DAMAGE. IN ADDITION, THE IMAGE

VERSIBLE EYE DAMAGE. IN ADDITION, THE IMAGE

PROJECTED BY THE FINDER IS HOT ENOUGH TO BURNPROJECTED BY THE FINDER IS HOT ENOUGH TO BURN

PROJECTED BY THE FINDER IS HOT ENOUGH TO BURN

SKIN OR CLOTHING.SKIN OR CLOTHING.

SKIN OR CLOTHING.

A telescope is an instrument that collects and focuses light. The nature of the

optical design determines how the light is focused. Some telescopes, known

as refractors, use lenses while others, known as reflectors, use mirrors. The

Schmidt-Cassegrain optical system (or SCT for short) uses a combination of

mirrors and lenses and is referred to as a compound or catadioptric telescope. This

unique design offers large diameter optics while maintaining very short tube

lengths, making them extremely portable. The Schmidt-Cassegrain system

consists of a zero power corrector plate, a spherical primary mirror, and a second-

ary mirror. Once light rays enter the optical system, they travel the length of the

optical tube three times.

Inside the optical tube you will notice a black tube (not illustrated) that extends

out from the center hole in the primary mirror. This is the primary baffle tube

and it prevents stray light from passing through to the eyepiece or camera.

A Word of CautionA Word of Caution

A Word of Caution

The Schmidt-The Schmidt-

The Schmidt-

CassegrainCassegrain

Cassegrain

Optical SystemOptical System

Optical System

Introduction • 3

Figure 1-1

This cross-sectional diagram shows the light path of the Schmidt-Cassegrain optical

system. Note that the light rays travel the length of the telescope tube three times,

making this a compact optical design. Note that the curve of the corrector plate is

greatly exaggerated.

4 • The G-9 1/4

ASSEMBLINGASSEMBLING

ASSEMBLING YY

YY

YOUROUR

OUROUR

OUR G - 9G - 9

G - 9G - 9

G - 9 1/4

AT POLARIS CAT POLARIS C

AT POLARIS C

The Celestron G-91/4is a standard 9.25" Schmidt-Cassegrain telescope on a

German equatorial mount. The Celestron G-91/4comes standard with

Starbright™ coatings, an enhanced multi-layer aluminum coating on the primary

and secondary mirrors for increased reflectivity. Also, the corrector plate is fully

coated to allow maximum light transmission. The Celestron G-91/4is shipped in

two boxes. One contains the telescope optical tube and is accompanied by a box

that contains the standard accessories, which are:

• 26mm Plossl Ocular 1-1/4"

• Visual Back 1-1/4"

• Star Diagonal 1-1/4"

• 6x30mm Finder and Bracket

• Lens Cap

The second box contains the tripod, equatorial mount and the hardware needed to

set it up. Included are the:

• CG-5 German Equatorial Mount

• Counterweight Bar

• Two Counterweights (11 lbs each)

• Declination (DEC) Slow Motion Knob

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

• Adjustable Aluminium Tripod

• Accessory Tray

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 G-9

1/4has 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.

Unpacking YourUnpacking Your

Unpacking Your

G-9 1/4G-9 1/4

G-9 1/4

The G-9 1/4 • 5

1. Lens Cover 8. Accessory Tray

2. Dovetail Bar Clamp Knob 9. Latitude Adjustment Screw

3. R.A. Lock Lever 10. Star Diagonal

4. Counterweight Shaft 11. Eyepiece

5. Counterweights 12. Finderscope

6. Tripod 13. Optical Tube

7. Leg Extention Clamp

Figure 2-1

The G-9The G-9

The G-9

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2

3

4

5

6

7

8

9

10

11

12

13

6 • The G-9 1/4

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.

Setting Up the TripodSetting Up the Tripod

Setting Up the Tripod

Adjusting the TripodAdjusting the Tripod

Adjusting the Tripod

HeightHeight

Height

Figure 2-2

Warning: The G-91/4is quite heavy. Because of this, great care should be taken when

adjusting the tripod height. If you need to make fine adjustments to the tripod while

the scope is mounted, be very careful because it is easy to accidentally knock the

system over!

Assembling the CG-5 Equatorial Mount

(#91515)

Tripod HeadTripod Head

Tripod Head

The G-9 1/4 • 7

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

There are three wing bolts that hold the accessory tray to the bracket.

1. Locate the three wing bolts.

2. Place the accessory tray over the bracket 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 bracket (see figure

2-3).

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

5. Tighten the wing bolts fully.

Attaching the AccessoryAttaching the Accessory

Attaching the Accessory

TrayTray

Tray

Figure 2-3Figure 2-3

Figure 2-3

WingWing

Wing

BoltBolt

Bolt

8 • The G-9 1/4

With the accessory tray in place, the tripod will be much more stable making it

easier to attach the mount and telescope.

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-5 mount is a German

equatorial mount that attaches 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 sinceDo NOT remove the screws since

Do NOT remove the screws sinceDo NOT remove the screws since

Do NOT remove the screws since

they are needed later for polar alignment.they are needed later for polar alignment.

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 NOTNOT

NOTNOT

NOT be

removed.

Attaching the EquatorialAttaching the Equatorial

Attaching the Equatorial

MountMount

Mount

Figure 2-4Figure 2-4

Figure 2-4

The G-9 1/4 • 9

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

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 (see figure 2-5).

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.

Figure 2-5Figure 2-5

Figure 2-5

10 • The G-9 1/4

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).

Figure2-6

Telescope

Mounting Screw

DEC Lock

Lever

RA Lock

Lever

Mounting Platform

DEC Slow Motion

Knob

Altitude Adjustment

Control

Polar Housing

Cover

Azimuth Adjustment

Controls

Declination Setting

Circle

R.A. Slow Motion

Knob

Mounting Platform

Safety Screw

R.A. Setting

Circle

The G-9 1/4 • 11

Attaching the Counterweight Bar and Counterweights

The last item to be mounted before the telescope tube is the counterweight bar and

counterweights. 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, itit

itit

it

threads into the mount opposite the telescopethreads into the mount opposite the telescope

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 counterweights.

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. Move it high enough

to allow room for the second weight (see figure 2-7).

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

6. Repeat this process for the second weight.

7. Replace the safety thumbscrew on the end of the counterweight bar. The

thumbscrew will prevent the counterweights from sliding off the bar should

they ever become loose.

Figure 2-7

12 • The G-9 1/4

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

mount.

•Before you attach the optical tube, fully tighten the right ascension andBefore you attach the optical tube, fully tighten the right ascension and

Before you attach the optical tube, fully tighten the right ascension andBefore you attach the optical tube, fully tighten the right ascension and

Before you attach the optical tube, fully tighten the right ascension and

declination clamps. This will prevent the telescope from movingdeclination clamps. This will prevent the telescope from moving

declination clamps. This will prevent the telescope from moving

suddenly once attached to the mount.suddenly once attached to the mount.

suddenly once attached to the mount.

1. Loosen the hand knob on the side of the CG-5 mount.

2. Slide the dovetail bar that is attached to the telescope onto the CG-5

mount (see figure 2-8).

3. Tighten the knob on the CG-5 mount to hold the telescope in place.

NOTE:NOTE:

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

that the corrector end of the telescope is pointing away from the ground at all

times.

Attaching the TelescopeAttaching the Telescope

Attaching the Telescope

to the Mountto the Mount

to the Mount

Figure 2-8

This illustration shows the correct mounting procedure for the optical tube onto the CG-5

mount. The dovetail slide bar has been attached to the telescope tube and is ready to

attach to the CG-5 mount.

The G-9 1/4 • 13

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 balance bracket thumbscrew is tight). The

counterweightbar will extend horizontally onthe opposite sideof the

mount (see figure 2-9).

2. Release the telescope — GRADUALLY — to see which way the telescope

“rolls.”

3. Loosen the set screw on one or both counterweights.

4. Move the counterweights to a point where they balance 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., star diagonal,

eyepiece, etc.) have been attached to the telescope. The correct procedure for attaching

these accessories is discussed in the section on “Telescope Basics.”

Balancing the Telescope

inR.A.

R.A. CLAMP

14 • The G-9 1/4

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. Slightly loosen the balance bracket thumbscrew and slide the telescope

eitherforward or backwarduntil it remainsstationary when theDEC clamp

is released. Do NOT let go of the telescope tube while the balance

bracket thumbscrew is loose.

6. Tighten the thumbscrew 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.

Balancing the Telescope

in DEC

Figure 2-10

As with R.A., the telescope should be balanced in DEC after all the standard accessories

(i.e., star diagonal, eyepiece, etc.) have been attached to the telescope.

The G-9 1/4 • 15

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-5 mount has a range of 40°, starting at 20°

going up to 60°.

For rough adjustments in azimuth, simply pick up the telescope and tripod and

move it until the R.A. axis is roughly pointed towards north. For fine adjust-

ments in azimuth:

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

housing. While standing behind the telescope, the knobs are on the front

ofthe mount.

•Turning the rightadjustment knob clockwisemoves the mounttoward 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.

Adjusting the Mount

inAltitude

Adjusting the Mount

inAzimuth

Figure 2-11

16 • The G-9 1/4

The entire telescope and mount can be picked up and carried outside for a

casual observing session. If, however, you want to transport your G-91/4 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 G-91/4"

telescope.

The equatorial mount does NOT have to be removed if you are transporting the

telescopeyourself. However, youmay want to remove thecounterweights from

thecounterweight bar to lighten themount.

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.

When not in use, your Celestron G-91/4 can be left fully assembled and set up.

However, all lens and eyepiece covers should be put back in place. The

opening to the rear cell 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

surfacesshould stillbe covered to prevent dustbuild-up.

Now that you have completed assembling your G-91/4, you are ready to begin

attaching the accessories. Please turn to the section on “Telescope Basics” for

moreinformation.

Disassembling and

Transporting Your

G-9 1/4

Storing Your G-9 1/4

What Next?

Telescope Basics • 17

TELESCOPE BASICS

Once your telescope has been fully assembled, you are ready to attach the accesso-

ries and have a look. This section deals with basic telescope operations that are

common to all Celestron Schmidt-Cassegrain telescopes.

There are several accessories that come standard with all the Celestron Schmidt-

Cassegrain telescopes. The installation and use of each of these is described in this

section.

TheVisual Back

The visual back is the accessory that allows you to attach all visual accessories to

the telescope. The G-9 1/4comes with the visual back installed. If it is not already on

the tube it can be attached as follows:

1. Remove the rubber cover on the rear cell.

2. Place the knurled slip ring on the visual back over the threads on the rear cell

(seefigure3-2).

3. Hold the visual back with the set screw in a convenient position and rotate the

knurledslipring clockwise until tight.

Once this is done, you are ready to attach other accessories, such as eyepieces,

diagonal prisms, etc.

If you want to remove the visual back, rotate the slip ring counterclockwise until it is

freeof the rearcell.

TheStarDiagonal

The star diagonal uses a mirror that reflects the light at a right angle to the light path

of the telescope. This allows you to observe in positions that are physically more

comfortable than if you were to look straight through. To attach the star diagonal:

1. Turn the set screw on the visual back until it no longer extends into (i.e., ob-

structs) its inner diameter of the visual back.

2. Slide the chrome portion of the star diagonal into the visual back (see figure 3-2).

3. Tighten the set screw to hold the star diagonal in place.

If you wish to change the orientation of the star diagonal, loosen the set screw on the

visual back until the star diagonal rotates freely. Rotate the diagonal to the desired

position and tighten the set screw.

Attachingthe

Accessories

Celestron G-9.25 User manual

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