Celestron Advanced GT Hand Control Supplementary Guide

The following is a supplemental addendum to the included instruction manual that
explains the new features of Celestron's Advanced Series Telescopes. Please refer to
this addendum for information concerning the new hand control features included with
your telescope. Refer to the owner's manual for step-by-step instruction on assembling
and using your telescope.

The Advanced Series GT, computerized version of each telescope has a hand controller designed to give you
instant access to all the functions that your telescope has to offer. With automatic slewing to over 40,000
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 computerized 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 telescope to use a selected star or object as an alignment position.

3. Direction Keys: Allows complete control of the telescope in any direction. Use the direction keys to

move the telescope to the initial alignment stars or for centering objects in the eyepiece.

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Figure 3-1

The Advanced GT Hand Control

4. Catalog Keys: The Advanced Series has keys on the hand control to allow direct access to each of the

catalogs in its database. The hand control contains the following catalogs in its database:

Messier – Complete list of all Messier objects.
NGC – Complete list of all the deep-sky objects in 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 Advanced GT database have

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

Named Stars

Named Objects

Double Stars

Variable Stars

Asterisms

CCD Objects

IC Objects

Abell Objects

Constellation

5. Info: Displays coordinates and useful information about objects selected from the Advanced GT

database.

6. Tour: Activates the tour mode, which seeks out all the best objects for the current date and time, and

automatically slews the telescope to those objects.

7. Enter: Pressing Enter allows you to select any of the Advanced GT functions and accept entered

parameters.

8. Undo: Undo will take you out of the current menu and display the prev ious 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 rates and user defined obj ects

and many others.

10. Scroll Keys:

the right side of the LCD when there are sub-menus below the displayed menu. Using these keys will
scroll through those sub-menus.

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

12. RS-232 Jack: Allows you to interface with a computer and control the telescope remotely.

Used to scroll up and down within any of the menu lists. A double-arrow will appear on

Common name listing of the brightest stars in the
sky.
Alphabetical listing of over 50 of the most popular
deep sky objects.
Numeric-alphabetical listing of the most visually
stunning double, triple and quadruple stars in the
sky.
Select list of the brightest variable stars with the
shortest period of changing magnitude.
A unique list of some of the most recognizable star
patterns in the sky.
A custom list of many interesting galaxy pairs, trios
and clusters that are well suited for CCD imaging
with the Advanced GT telescope.
A complete list of all the Index Catalog deep-sky
objects.
A custom list of the Abell Catalog deep-sky
galaxies.
A complete list of all 88 constellations.

Hand Control Operation

This section describes the basic hand control procedures needed to operate the Advanced GT Series Telescopes.
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 utilities functions
such as calibrating your mount, polar alignment and backlash compensation.

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In order for the telescope to accurately point to objects in the sky, it must first be aligned with 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. There are many ways to alig n your telescope with the sky depend ing on what
information the user is able to provide: Two Star Align uses the entered time/location information and allows
the user to select which two alignment stars the telescope will automatically slew to. One Star Align uses the
same time/location information but only uses one star for alignment. Solar System Align will display a list of
visible daytime objects (planets and the moon) available to align the telescope. Quick-Align will ask you to
input all the same information as you would for the other Alignment procedures. However, instead of slewing
to the alignment stars for centering and alignment, the telescope bypasses this step and simply models the sky
based on the information given. Finally, Last Alignment restores your last saved star alignment and switch
position. Last Alignment also serves as a good safeguard in case the telescope should lose power.

SSttaarrttuupp PPrroocceedduurree

Before any of the described alignments are performed, the telescope mount needs to be positioned so that the
index marks are aligned on both the right ascension and declination axes (see Fig 2-8).
Once the index position has been set, the hand control will display the last entered date and time information
stored in the hand control. Once the telescope is powered on:

1. Press ENTER begin the alignment process.

2. The hand control will ask the user to set the mount to its index position. Move the telescope mount,

either manually or with the hand control, so that the index marked in both R.A. and Dec are aligned
(see Fig 2-8). Press Enter to continue.

3. The hand control will then display the last entered local time, date, time zone, longitude an d latitude.

• Use the Up/Down keys (10) to view the current parameters.

• Press ENTER to accept the current parameters.

• Press UNDO to enter current date and time information into the hand control. The following

information will be displayed:

Location - The hand control 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:

 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 eith er internationa l 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.

 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.

 Use the Up and Down Scroll buttons to choose your current state (or co untry if International lo cations

was selected) from the alphabetical listing and press ENTER.

 Use the Up and Down Scroll buttons to choose the closest city to yo ur location fro m the displayed list

and press ENTER.

Time - Enter the current local time for your area. You can enter either the local time (i.e. 08:00),
or you can enter military time (i.e. 20:00 ).

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

• Choose between Standard time or Daylight Savings time. Use the Up and Down scroll

buttons (10) to toggle between options.

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

to scroll through the choices. Refer to Time Zone map in Appendix for more information.

Date - Enter the month, day and year of your observing session.

4. Select one of the alignment methods as described below.

Note: If incorrect information is entered into the hand control, the UNDO button acts like a back space button
allowing the user to re-enter the correct data.

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Two-Star Align allows the user to select two stars on which to align the telescope. To align your telescope
using the Two-Star Align method:

1. Select Two-Star Align from the alignment choices given. Based on the date and time information

entered, the hand control will automatically select and display a bright star that is above the horizon.

• Press ENTER to select this star as your first alignment

star.

• If for some reason the chosen star is not visible

(perhaps behind a tree or building) press UNDO to
have the hand control automatically select the next
brightest star.

• Or you can use the Up/Down keys to browse the entire

Named Star list and select any one of over two hundred
alignment stars.

• The hand control will only display stars on one side of

the Meridian. To display alignment stars on the
opposite side of the Meridian, simply press the MENU
button before selecting your first alignment star. By
default, Meridian filtering is enabled with the side of
the Meridian that has the largest number of stars above
the horizon. Meridian filtering is indicated in the upper
right hand corner of the LCD display with an “E” (East)
or “W” (West). If nothing appears in the corner of the
LCD, Meridian filtering is not enabled.

Mount Calibration

After a Two Star Alignment is
successfully completed, the hand
control will ask if you wish to add
calibration stars.

Adding calibration stars is necessary
to calculate and compensate for
"cone" error inherent in all German
equatorial mounts. Cone error is the
inaccuracy that results from the
optical tube not being exactly
perpendicular to the mount’s
declination axis. The telescope is
able to automatically determine the
cone error value by always using
calibration stars on the opposite
side of the Meridian from the
alignment stars. (see Figure 3-2)

2. Once the telescope is finished slewing to your first alignment

star, the display will ask you to use the arrow buttons to align the selected star with the cross hairs in
the center of the finderscope. When centered in the
finder, press ENTER.

3. 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.

4. After the first alignment star has been entered the hand

control will automatically select a second alignment
star and have you repeat this procedure for that star.

When the telescope has been aligned on both stars the
display will ask you if you wish to add any additional
calibration stars. Calibration stars are used to improve the
pointing accuracy of your telescope by compensating for
subtle optical-mechanical misalignments between the
telescope optics and the mount. Therefore it is usually a
good idea to add at least two additional ca libration stasr to
improve the telescope’s all-sky pointing accuracy. If you
choose not to add any additional calibration stars you can
always add them later after a successful alignment has been
completed (see Improving Pointing Accuracy section
below).

The Meridian is an imaginary line in the sky
that starts at the North celestial pole and
ends at the South celestial pole and passes
through the zenith. If you are facing South,
the meridian starts from your Southern
horizon and passes directly overhead to the
North celestial pole.

Figure 3-2

5. Press ENTER to select a calibration star. Select a star the same way you did with the first two

alignments stars and press ENTER. You will notice that all the calibration stars displayed are located

on the opposite side of the side of the sky (Meridian) as the original alignment stars. This is essential
for an accurate calibration of the mount.

Finally you can choose to continue to add add itional calibration stars or Press UNDO to complete the
alignment.

Tips for adding calibration stars:

• It is recommended that users add at least two calibration stars for optimal point accuracy.

• Calibration stars that are near the poles are intentionally filtered out because they can result in a

less accurate calibration.

• Although it is not be necessary to use calibration stars if the telescope mount has not been moved

since its original alignment/calibration, it may be necessary to add calibration stars if the optical
tube has been removed for any reason.

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One-Star Alignment works much the same way as Two-Star Align but uses only a single star in the sky for
alignment. This method of alignment is not as accurate as the two-star alignment and is recommended only for
telescopes that are permanently and accurately polar aligned.

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Solar System Align is designed to provide excellent tracking and GoTo performance by using solar system
objects (Sun, Moon and planets) to align the telescope with the sky. Solar System Align is a great way to align
your telescope for daytime viewing as well as a quick way to align th e telescope for nighttime observing.

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.

1. Select Solar System Align from the alignment options.

2. The SELECT OBJECT message will appear in the top row of the display. Use the Up and Down scroll keys (10) to

select the daytime object (planet, moon or sun) you wish to align. Press ENTER.

3. Use the direction arrow buttons to carefully center the object in the finderscope. Press ENTER when centered.

4. Then, center the object in the eyepiece and press ALIGN.

Once in position, the telescope will model the sky based on this information and display Alignment
Successful.

Tips for Using Solar System Align

• For safety purposes, the Sun will not be displayed in any of the hand control’s customer object lists unless it is

enabled from the Utilities Menu. To allow the Sun to be displayed on the hand control, do the following:

1. Press the UNDO button until the display reads “Advanced GT”

2. Press the MENU button and use the Up and Down keys to select the Utilities menu. Press ENTER.

3. Use the UP and Down keys to select Sun Menu and press ENTER.

4. Press ENTER again to allow the Sun to appear on the hand control display.

The Sun can be removed from the display by using the same procedure as above.

• To improve the telescope pointing accuracy, you can add alignment stars as described in the Improving Pointing

Accuracy section below.

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Quick-Align uses all the date and time information entered at startup to align the telescope. However, instead of slewing to
the alignment stars for centering and alignment, the telescope bypasses this step and simply models the sky based on the