Celestron NexStar 80GTL User Manual

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

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ASSEMBLY.......................................................................................................................................................................5

Assembling the NexStar..................................................................................................................................................6

Attaching the Telescope to the Tripod.........................................................................................................................7

Balancing the Telescope tube......................................................................................................................................7

The Erect Image Diagonal........................................................................................................................................... 7

The Eyepiece...............................................................................................................................................................8

Focusing......................................................................................................................................................................8

The Star Pointer Finderscope ......................................................................................................................................8

Star Pointer Installation...........................................................................................................................................9

Star Pointer Operationn ...........................................................................................................................................9

Using your Solar Filter.............................................................................................................................................. 10

HAND CONTROL ..........................................................................................................................................................11

Attaching the Hand Control.......................................................................................................................................11

Powering the NexStar................................................................................................................................................11

The Hand Control......................................................................................................................................................11

Hand Control Operation................................................................................................................................................13

Alignment Procedure.................................................................................................................................................13

Auto-Align ................................................................................................................................................................13

Two Star Alignment..................................................................................................................................................14

Quick-Align...............................................................................................................................................................15

NexStar Re-Alignment..............................................................................................................................................15

Object Catalog...............................................................................................................................................................16

Selecting an Object....................................................................................................................................................16

Slewing to an Object .................................................................................................................................................16

Tour Mode.................................................................................................................................................................16

Direction Buttons ..........................................................................................................................................................17

Rate Button................................................................................................................................................................17

Set Up Procedures.........................................................................................................................................................17

Tracking Mode..........................................................................................................................................................17

Tracking Rate............................................................................................................................................................18

View Time-Site .....................................................................................................................................................18

Sidereal Time ........................................................................................................................................................ 18

Filter Limits...........................................................................................................................................................18

RS-232...................................................................................................................................................................18

User Defined Objects ............................................................................................................................................18

Get RA/DEC .............................................................................................................................................................19

Get Alt-Az................................................................................................................................................................. 19

Goto R.A/Dec............................................................................................................................................................19

Goto Alt-Az...............................................................................................................................................................19

Utility Features..............................................................................................................................................................19

Setup Time-Site................................................................................................................

Anti-backlash ........................................................................................................................................................19

Slew Limits ........................................................................................................................................................... 20

Direction Buttons ..................................................................................................................................................20

Light Control.........................................................................................................................................................20

Select Model..........................................................................................................................................................20

TELESCOPE BASICS....................................................................................................................................................22

Focusing....................................................................................................................................................................22

Image Orientation......................................................................................................................................................22

Calculating Magnification .........................................................................................................................................22

Determining Field of View........................................................................................................................................23

General Observing Hints...........................................................................................................................................23

CELESTIAL OBSERVING ...........................................................................................................................................24

Observing the Moon..............................................................................................................................................24

Lunar Observing Hints..........................................................................................................................................24

Observing the Planets............................................................................................................................................ 24

Planetary Observing Hints..................................................................................................................................... 24

.....................................19

Observing the Sun .................................................................................................................................................24

Solar Observing Hints ...........................................................................................................................................25

Observing Deep Sky Objects.................................................................................................................................25

Terrestrial (Land) Viewing....................................................................................................................................25

Terrestrial (Land) Viewing Hints ..........................................................................................................................25

Seeing Conditions..................................................................................................................................................25

Transparency .........................................................................................................................................................25

Sky Illumination.................................................................................................................................................... 26

Seeing.................................................................................................................................................................... 26

TELESCOPE MAINTENANCE....................................................................................................................................27

Care and Cleaning of the Optics....................................................................................................................................27

OPTIONAL ACCESSORIES.......................................................................................................................................28

APPENDIX A - TECHNICAL SPECIFICATIONS ...................................................................................................30

APPENDIX B – GLOSSARY OF TERMS ...................................................................................................................31

APPENDIX C – RS 232 CONNECTION ......................................................................................................................34

Communication Protocol:......................................................................................................................................34

APPENDIX D – TIME ZONE MAPS ...........................................................................................................................35

SKY MAPS ......................................................................................................................................................................37

Congratulations on your purchase of the Celestron NexStar! The NexStar ushers in a whole new generation of computer automated technology. Simple and friendly to use, the NexStar is up and running after locating just two alignment stars. It’s the perfect combination of power and portability. If you are new to astronomy, you may wish to start off by using the NexStar's built-in Sky Tour feature, which commands the NexStar to find the most interesting objects in the sky and automatically slews to each one. Or if you are an experienced amateur, you will appreciate the comprehensive database of over 4,000 objects, including customized lists of all the best deep-sky objects, bright double stars and variable stars. No matter at what level you are starting out, the NexStar will unfold for you and your friends all the wonders of the Universe.

Some of the many standard features of the NexStar include:

• Incredible 4°/second slew speed.

• Fully enclosed motors and optical encoders for position location.

• Computerized hand controller with 4,000 object database.

• Storage for programmable user defined objects; and

• Many other high performance features!

The NexStar’s deluxe features combined with Celestron’s legendary optical standards give amateur astronomers one of 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 NexStar, so you should keep this manual handy until you have fully mastered your telescope’s operation. The NexStar hand control has built-in instructions to guide you through all the alignment procedures needed to have the telescope up and running in minutes. Use this manual in conjunction with the on-screen instructions provided by the hand control. 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 NexStar 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.

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• Never look directly at the sun with the naked eye or with a telescope (unless using your Celestron solar filter).

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

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

• Never leave the telescope unsupervised, either when children are present or adults who may not be familiar

Permanent and irreversible eye damage may result.

the telescope and any accessories attached to it.

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

with the correct operating procedures of your telescope.

The NexStar 80GTL

Refractor Telescope

1 Objective Lens 7 Focuser Knob

2 Fork Arm 8 Erect Image Diagonal - 90˚

3 Power Outlet 9 Eyepiece

4 Tripod 10 Star Pointer Finderscope

5 Hand Control 11 Optical Tube

6 Accessory Tray w/ hand control holder 12 Tube Ring Clamp

The NexStar comes partially assembled and can be operational in a matter of minutes. The NexStar is conveniently packaged in one reusable shipping carton that contains the following accessories:

NexStar 80 GTL

25mm & 10mm Eyepieces – 1¼"

1¼" Erect Image Diagonal Star Pointer Finderscope and Mounting Bracket Deluxe Accessory Tray Battery Pack Solar Filter

The Sky™ Level 1 Astronomy Software Telescope Control Software NexStar Hand Control w/ Object Database

Assembling the NexStar

Your NexStar comes in three major sections: the optical tube, fork arm and the tripod. These sections can be attached in seconds using the quick release coupling screw located under the tripod mounting platform. Remove all of the accessories from their individual boxes. Remember to save all of the containers so that they can be used to transport the telescope. Before attaching the visual accessories, the telescope tube should be mounted to its tripod. First, install the accessory tray onto the tripod legs:

Optical Tube

Tripod Mounting Platform

Fork Arm

Base

Figure 2-1

1. Remove the tripod from the box and spread the legs apart until the center leg brace is fully extended.

2. Locate the accessory tray, and place it on top of the tripod center support brace in between the tripod legs (see figure 2-

2).

Coupling Screw

3. From underneath the tripod support brace, thread the locking bolt into the hole in the center of the accessory tray. Do not over tighten.

The accessory tray has a built-on hand control holder protruding from the side. The back of the hand control has an opening that slides over the clip on the inside of the holder.

It is a good idea to adjust the height of the tripod before attaching the fork arm and tube. Minor adjustments can be made later. To adjust the height of the tripod legs:

Loosen the tripod leg locking bolt located on the side of each leg.

1. Slide the inner portion of each leg down 6" to 8" inches.

2. Tighten the tripod locking bolts to hold each leg in place.

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With the tripod properly assembled, the telescope tube and fork arm can easily be attached using the quick release coupling screw located underneath the tripod mounting platform:

1. Hold the telescope tube assembly by the fork arm and place the fork arm base inside the tripod mounting platform. See Figure 2-1.

2. Thread the coupling screw into the hole at the bottom of the fork arm base and hand tighten.

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To ensure optimal performance from your NexStar 80 it is necessary to properly balance the telescope tube inside the tube ring. To assist in balancing the tube, the NexStar 80 has a Solar Warning sticker to help you position the tube. To balance the tube, simply loosen the tube clamp ring locking screw and slide the telescope tube forward or back until the edge of the tube ring is aligned with the line at the top of the Solar Warning sticker. (see Figure 2-3)

Your NexStar is fully assembled and is ready to attach the accessories.

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The diagonal diverts the light at a right angle from the light path of the telescope. For astronomical observing, this allows you to observe in positions that are more comfortable than if you were to look straight through the tube. For daytime viewing, the diagonal uses an erecting prism that allows you see land objects right-side-up To attach the diagonal:

1. Turn the thumbscrew on the eyepiece adapter at the end of the focuser barrel until it no longer extends into (i.e., obstructs) the inner diameter of the focus barrel. Remove the protective dust cap from the focuser barrel.

Accessory Tray

Figure 2-2 – The Accessory Tray/ Hand Control

Holder

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Locking Bolt (underneath Accessory Tray)

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2. Slide the chrome portion of the diagonal into the eyepiece adapter.

3. Tighten the thumbscrew on the eyepiece adapter to hold the diagonal in place.

If you wish to change the orientation of the star diagonal, loosen the thumbscrew on the eyepiece adapter until the star diagonal rotates freely. Rotate the diagonal to the desired position and tighten the thumbscrew.

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The eyepiece, is the optical element that magnifies the image focused by the telescope. The eyepiece fits either directly into the focuser or into the diagonal. To install the eyepiece:

Eyepiece

Star Pointer

1. Loosen the thumbscrew on the diagonal so it does not obstruct the inner diameter of the barrel. Remove the protective dust cap from the diagonal's barrel.

2. Slide the chrome portion of the low power 25mm eyepiece into the diagonal.

3. Tighten the thumbscrew to hold the eyepiece in place.

To remove the eyepiece, loosen the thumbscrew on the diagonal and slide the eyepiece out.

Focus Knob

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 power or magnification; and the shorter the focal length (i.e., the smaller the number) the higher the magnification.

Erect Image Diagonal

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Eyepiece Adapter

Generally, you will use low-to-moderate power when viewing. For more information on how to determine power, see the section on “Calculating Magnification.”

Barrel diameter is the diameter of the barrel that slides into the star diagonal or focuser. The NexStar uses eyepieces with a standard 1-1/4" barrel diameter.

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To focus your telescope, simply turn either of the focus knobs on the sides of the focuser (see figures 2-4). Turn the focus knob until the image is sharp. Once sharp, turn the knob towards you to focus on an object that is closer than the one you are currently observing. Turn the knob away from you to focus on a more distant object than the one you are currently observing.

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The Star Pointer is the quickest and easiest way to point your telescope exactly at a desired object in the sky. It's like having a laser pointer that you can shine directly onto the night sky. The Star Pointer is a zero

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magnification pointing tool that uses a coated glass window to superimpose the image of a small red dot onto the night sky. While keeping both eyes open when looking through the Star Pointer, simply move your telescope until the red dot, seen through the Star Pointer, merges with the object as seen with your unaided eye.

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The red dot is produced by a light-emitting diode (LED); it is not a laser beam and will

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not damage the glass window or your eye. The Star Pointer comes equipped with a variable brightness control, two axes alignment control and mounting brackets. Before the Star Pointer is ready to be used, it must be attached to the telescope tube and properly aligned:

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1. Slide the Star Pointer bracket into the dovetail mounting platform on top of the focuser assembly (see figure 2-6).

2. Orient the Star Pointer so that the sight tube is facing towards the front of the tube.

3. Secure the Star Pointer bracket by tightening the thumb screw on the mounting platform.

Star Pointer Operation

The star pointer is powered by a long life 3-volt lithium battery (#CR2032) located underneath the front portion of the Star Pointer. Like all finderscopes, the Star Pointer must be properly aligned with the main telescope before it can be used. This is a simple process using the azimuth and altitude control knobs located on the side and bottom of the Star Pointer. The alignment procedure is best done at night since the LED dot will be difficult to see during the day. Note: Before using the StarPointer, you must first remove the

protective plastic cover over the battery (see figure 2-7).

1. To turn on the Star Pointer, rotate the variable brightness control (see figure 2-5)

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clockwise until you here a "click". To increase the brightness level of the red dot, continue rotating the control knob about 180º until it stops.

2. Locate a bright star or planet and center it in a low power eyepiece in the main telescope.

3. With both eyes open, look through the glass window at the alignment star.

Protective

Cover

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If the Star Pointer is perfectly aligned, you will see the red LED dot overlap the alignment star. If the Star Pointer is not aligned, take notice of where the red dot is relative to the bright star.

Battery

Red

Alignment

Dot

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Azimuth adjustment Knob

4. Without moving the main telescope, turn the Star Pointer's azimuth and altitude alignment controls (see figure 2-5) until the red dot is directly over the alignment object.

If the LED dot is brighter than the alignment star, it may make it difficult to see the star. Turn the brightness control counterclockwise, until the red dot is the same brightness as the alignment star. This will make it easier to get an accurate alignment. The Star Pointer is now ready to be used.

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Solar observing is one of the most rewarding forms of celestial observations. Yet, because the Sun is so bright, special precautions must be taken to ensure your safety and protect your equipment. Therefore, read these instructions through

completely BEFORE

you attempt to use your solar filter.

A Word of Caution

Never look through the StarPointer finderscope when pointed at the Sun.

About the Filter

The Celestron AstroSolar™ solar filter by Baader allows direct observations of the Sun in complete safety. The filter, which transmit .00001% of the Sun’s visible light, allows you to see the outer atmosphere of the Sun including such features as sunspots, granules and faculae. The material used to make these filters is a precision engineered, high-strength polymer that is ion implanted and metallized with a tough, neutral color layer on both sides of the film.

The Appearance

One of the first things you may notice when you remove your solar filter from the box is that the film is slightly wrinkled. This is the way the filter is supposed to look. The best resolution is obtained when the material is slightly relaxed or wrinkled.

Installation and Use

Before installing the solar filter, you should always inspect the surface of the filter

Filter Cell

for holes or other damage. To inspect the filter, hold it up to a bright light source (other than the Sun) like a white wall reflecting sunlight or a patch of blue sky away from the sun. Look for any light that may be passing through the filter. If any light is visible, the filter should NOT be used.

To install the filter, point your telescope away from the Sun and remove the lens cap. Now, place the solar filter over the front lens or opening of the telescope. Push the filter cell until the inside of the filter cell is flush against the end of the tube. The filter should be tight enough so that it will NOT fall off when the telescope is

AstroSolar Filter

Material

pointed toward the ground.

Once the solar filter is securely in place you are ready for your first look. To do so,

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point the telescope in the general direction of the Sun. Now, look at the shadow of the telescope tube, which will indicate how close you are to the Sun. Look closely at the shadow cast by the StarPointer finderscope. When you see light shining through the StarPointer’s sight tube you are approaching the Sun. The more elongated the light, the farther away from the Sun you are pointing. When the light is circular, you should be pointing directly at the Sun. Look through a low power eyepiece to see if the solar image is there. If not, slowly sweep around until the sun comes into the field.

Cleaning and Storage

To clean the filter, use a photographic cleaning brush to remove dust and other debris. Never rub the filter. Be sure that when handling your solar filter not to touch the filter itself. When not in use, store your filter in its box. Place the box in a dry, warm environment that is relatively dust free. Moisture on the filter can and will degrade the performance. Do not use the filter if AstroSolar film is punctured in any way.

For tips on viewing the Sun through your filter, see the Celestial Observing section of this manual.

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The NexStar GT hand control has a phone jack type connector at the end of its cord. Plug the phone jack connector into the outlet at the base of the telescope’s fork arm. Push the connector into the outlet until it clicks into place and place the hand control into its holder as described previously in the Assembly section of the manual.

Hand Control Outlet

Power Outlet

Battery Pack

Figure 3-1 – The NexStar GT Outlets

Note

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The NexStar GT can be powered by the supplied battery pack or an optional 12v AC adapter. The power pack requires 8 user supplied AA size alkaline batteries. To power the NexStar, insert the batteries into the battery pack and plug the round post into the 12v outlet located on the side of the fork arm. Once the battery pack is plugged in, the NexStar will power on and the red backlight on the hand control display will come on.

In case of a loss of power, the optical tube can be moved by hand. However, when powered on, the telescope should always be controlled via the hand control. The NexStar will lose its star alignment if moved by hand when powered on.

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The NexStar GT's hand controller is designed to give you instant access to all the functions the NexStar has to offer. With automatic slewing to over 4,000 objects, and common sense menu descriptions, even a beginner can master its variety of features in just a few observing sessions. Below is a brief description of the individual components of the NexStar GT hand controller:

1. Liquid Crystal Display (LCD) Window: Has a dual-line, 16 character display screen that is backlit for comfortable viewing of telescope information and scrolling text.

2. Align: Instructs the NexStar to use a selected star or object as an alignment position.

3. Direction Keys: Allows complete control of the NexStar in any direction. Use the direction keys to center objects in the StarPointer finderscope and eyepiece.

4. Catalog Keys: The NexStar has a key on the hand control to allow direct access to each of the catalogs in its 4,000+ object database. The NexStar contains the following catalogs in its database:

Messier – Complete list of all Messier objects. NGC – Many of the brightest deep sky objects from the Revised New General Catalog. Caldwell – A combination of the best NGC and IC objects.

Planets - All 8 planets in our Solar System plus the Moon. Stars – A compiled list of the brightest stars from the SAO catalog. List – For quick access, all of the best and most popular objects in the NexStar database have been broken down

into lists based on their type and/or common name:

Named Stars Common name listing of the brightest stars in the sky. Named Objects Alphabetical listing of over 50 of the most popular deep

sky objects.

Double Stars Alphabetical listing of the most visually stunning double,

triple and quadruple stars in the sky.

Variable Stars Select list of the brightest variable stars with the shortest

period of changing magnitude.

Asterisms A unique list of some of the most recognizable star

patterns in the sky.

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5. Info: Displays coordinates and useful information about objects selected from the NexStar database.

6. Tour: Activates the tour mode, which seeks out all the best objects for a given month and automatically slews the NexStar to those objects.

7. Enter: Pressing Enter allows you to select any of the NexStar functions, accept entered parameters and slew the telescope to displayed objects.

8. Undo: Undo will take you out of the current menu and display the previous level of the menu path. Press Undo repeatedly to get back to a main menu or use it to erase data entered by mistake.

9. Menu: Displays the many setup and utilities functions such as tracking rate and user defined objects and many others.

10. Scroll Keys: Used to scroll up and down within any of the menu lists. A double arrow symbol on the right side of the LCD indicates that the scroll keys can be used to view additional information.

11. Rate: Instantly changes the rate of speed of the motors when the direction buttons are pressed.

12. RS-232 Jack: Allows use with a computer and software programs for point and click slewing capability.

Hand Control Operation

This section describes the basic hand control procedures needed to operate the NexStar. These procedures are grouped into three categories: Alignment, Setup and Utilities. The alignment section deals with the initial telescope alignment as well as finding objects in the sky; the setup section discusses changing parameters such as tracking mode and tracking rate; finally, the last section reviews all of the utility functions such as adjusting the telescopes slew limits and backlash compensation.

Important

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In order for the NexStar to accurately point to objects in the sky, it must first be aligned with two known positions (stars) in the sky. With this information, the telescope can create a model of the sky, which it uses to locate any object with known coordinates.

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Auto-Align is the easiest way to get your NexStar aligned and ready to observe. Even if you do not know a single star in the sky, the NexStar will align itself by guiding the user through the alignment procedure by asking for basic information like the date, time and location. The NexStar will then automatically choose two stars for alignment and roughly center the stars in the field of view of the Star Pointer. Before the telescope is ready to be aligned, it should be set up in an outside location with all accessories (eyepiece, diagonal and Star Pointer) attached and lens cover removed as described in the Assembly section of the manual.

1. Once the NexStar is powered on the display will read NexStar Ready. Press ENTER to begin alignment.

The first time that the NexStar is used, it will request information to help identify the model of telescope. Once powered on, the hand control will display the message different NexStar models. Press ENTER when NexStar 80 is displayed on the hand control. This information will be retained for future use and will not be displayed again. If for some reason the incorrect model was selected or you wish to use your hand control on a different NexStar model, the Select Model utility feature allows you to re-select the proper NexStar model from the displayed list (see Select Model later in this section).

2. Use the Up and Down scroll keys to select AutoAlign if it is not already displayed, and press ENTER.

3. The telescope will then ask you to use the direction keys (3) to level the telescope tube and point the front of the telescope towards north. North can be found by using the compass affixed to the accessory tray (see figure 3-3). Use the hand control to point the telescope in the same direction as indicated by the red pointer on the compass. Alignment only needs to be approximate, however a close alignment will make the auto alignment more accurate. Once the telescope is in the north and level position, press ENTER.

4. The hand control display will then ask for the following information:

Select Model

Select ModelSelect Model

. Use the Up and Down menu keys (10) to scroll through the

Location - The NexStar will display a list of cities to choose from.

Choose the city from the database that is closest to your current observing site. The city you choose will be remembered in the hand controls memory so that it will be automatically displayed the next time an alignment is done. Alternatively, if you know the exact longitude and latitude of your observing site, it can be entered directly into the hand control and remembered for future use as well. To choose a location city:

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FindingNorth and Level Position

Y Use the Up and Down scroll keys to choose between City Database and Custom Site. City Database will allow you to

select the closest city to your observing site from a list of either international or U.S. location. Custom Site allows you to enter the exact longitude and latitude of your observing site. Select City Database and press ENTER.

Y The hand control will allow you to choose from either U.S. or international locations. For a listing of U.S. locations by

state and then by city, press ENTER while United States is displayed. For international locations, use the Up or Down scroll key to select International and press ENTER.

Y To display a list of local cities, first select your state from the alphabetical listing (or a list of countries if International

locations was selected) and press ENTER.

Y Choose the closest city to your location from the displayed list and press ENTER.

Time - Enter the current time for your area. You can enter either the local time (i.e. 8:00), or you can enter military time (i.e.

20:00).

Y Select PM or AM. If military time was entered, the hand control will bypass this step.

Y Choose between Standard time or Daylight Savings time. Use the Up and Down scroll buttons (10) to toggle between

options.

Y Select the time zone that you are observing from. Again, use the Up and Down buttons (10) to scroll through the

choices. For time zone information, refer to the Time Zone map in the appendix of this manual.

Helpful

Hints

Observing

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Date - Enter the month, day and year of your observing session. The display will read: mm/dd/yy.

If the wrong information has been input into the hand control, the UNDO button will act as a backspace allowing the user

to re-enter information.

The next time that your NexStar is auto aligned, the hand control will automatically display the last location (either a city or longitude/latitude) that was entered. Press ENTER to accept these parameters if they still apply. Pressing the UNDO button will allow you to go back and select a new city location or longitude/latitude.

Y Based on this information, the NexStar will automatically select a bright star that is above the horizon and slew

towards it. At this point the telescope is only roughly aligned, so the alignment star should only be close to the field of view of the Star Pointer finder. Once finished slewing, the display will ask you to use the arrow buttons to align the selected star with the red dot in the center of the Star Pointer. If for some reason the chosen star is not visible (perhaps behind a tree or building) you can press UNDO to select and slew to a different star. Once centered in the finder, press ENTER. The display will then instruct you to center the star in the field of view of the eyepiece. When the star is centered, press ALIGN to accept this star as your first alignment star. (There is no need to adjust the slewing rate of the motors after each alignment step. The NexStar automatically selects the best slewing rate for aligning objects in both the Star Pointer and the eyepiece). After the first alignment star has been entered the NexStar will automatically slew to a second alignment star and have you repeat the same procedure for that star. When the telescope has been aligned to both stars the display will read

If the wrong star was centered and aligned to, the NexStar display will read

Alignment Succ

Alignment Successful

Alignment SuccAlignment Succ

essful

essfulessful

, and you are now ready to find your first object.

Align Failed

Align FailedAlign Failed

. Press UNDO to begin

the alignment procedure again.

If you are not sure if the correct star was centered, always remember that the alignment star will be the brightest star nearest the field of view of the finder. There may be other fainter stars visible that are closer to the center of the Star Pointer, but the actual alignment star will be obviously brighter than any other star in the area.

When centering the alignment stars in the eyepiece, use the up arrow button and the right arrow button on the hand control. Centering the star from this direction will eliminate much of the backlash between the gears and assure the most accurate alignment possible.

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With the two-star alignment method, the NexStar requires the user to know the positions of only two bright stars in order to accnurately align the telescope with the sky and begin finding objects. Here is an overview of the two-star alignment procedure:

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Celestron NexStar 80GTL User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual