ADDENDUM TO PRODUCT MANUAL
Your Celestron NexStar 8i Special Edition now comes with many new enhanced features including the patented SkyAlign alignment procedure. SkyAlign 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 have you aligned in minutes by asking for basic information like the date, time and location. Then you simply need to aim the telescope to any three bright celestial objects in the sky. Since SkyAlign requires no knowledge of the night sky it is not necessary to know the name of the stars at which you are aiming. You may even select a planet or the moon. The NexStar is then ready to start finding and tracking any of the objects in its 40,000+ object database. In addition to SkyAlign, the NexStar has other advanced features like SolarSystem align, One-Star Align and added functions like Sun Menu, Scrolling Menu and Constellation Tour. Please use this addendum in conjunction with your owner's manual as reference for all your telescope's new and existing features. To download a copy of the most current manual for this telescope, please go to the NexStar i series product page at www.celestron.com
Alignment Procedure In order for the NexStar to accurately point to objects in the sky, it must first be aligned to 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 align the NexStar with the sky depending on what information the user is able to provide: SkyAlign uses your current date, time and city to create an accurate model of the sky. Then the user can simply point the telescope to any three bright celestial objects to accurately align the telescope with the sky. OneStar Align is the same as the Two-Star Alignment method described in your owner's manual, however only requires you to align to one known star. Although not as accurate as the other alignment methods, One-Star Align is the quickest way to find and track bright planets and objects in Altazimuth mode. Finally, Solar System Align will display a list of visible daytime objects (planets and the moon) available to align the telescope. Each alignment method is discussed in detail below.

Definition

"Altazimuth" or "Alt-Az" refers to a type of mounting that allows a telescope to move in both altitude (up and down) and azimuth (left and right) with respect to the ground. This is the simplest form of mounting in which the telescope is attached directly to a tripod.
SkyAlign SkyAlign 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 have you aligned in minutes by asking for basic information like the date, time and location. Then you simply need to aim the telescope to any three bright celestial objects in the sky. Since SkyAlign requires no knowledge of the night sky it is not necessary to know the name of the stars at which you are aiming. You may even select a planet or the moon. The NexStar is then ready to start finding and tracking any of the objects in its 4,000+ object database. Before the telescope is ready to be aligned, it should be set up in an outside location with all accessories (eyepiece, diagonal and finderscope) attached and lens cover removed as described in the Assembly section of the manual. To begin SkyAlign: 1. Power on the NexStar by flipping the switch located on the side of the fork arm, to the "on" position. Once turned on the hand control display will say NexStar SE. Press ENTER to choose SkyAlign. Pressing the ALIGN key will bypass the other alignment options and the scrolling text and automatically begins Sky Align. Once SkyAlign has been selected, the hand control will display Enter if OK, Undo to edit and Saved Site. The bottom line of the LCD will display either the current time or the time when you last used the telescope. Since this is your first time using the NexStar , press UNDO to enter current time/site information.

The hand control display will then ask for the following information: 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: 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. 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 country if International locations was selected) from the alphabetical listing and press ENTER. Use the Up and Down Scroll buttons to choose the closest city to your location from the displayed list and press ENTER. 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).

Time -

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

Use the arrow buttons on the hand control to slew (move) the telescope towards any bright celestial object in the sky. Align the object with the red dot of the finderscope and press ENTER. If the finderscope has been properly aligned with the telescope tube, the alignment star should now be visible inside the field of view of the eyepiece. The hand control will ask that you center the bright alignment star in the center of the eyepiece and press the ALIGN button. This will accept the star as the first alignment position. (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 finderscope and the eyepiece). For the second alignment object, choose a bright star or planet as far as possible from the first alignment object. Once again use the arrow button to center the object in the finderscope and press ENTER. Then once centered in the eyepiece press the ALIGN button. Repeat the process for the third alignment star. When the telescope has been aligned to the final stars, the display will read "Match Confirmed". Press UNDO to display the names of the three bright objects you aligned to, or press ENTER to accept these three objects for alignment. You are now ready to find your first object.
Tips for Using SkyAlign Remember the following alignment guidelines to make using SkyAlign as simple and accurate as possible.
Be sure to level the tripod before you begin alignment. The time/site information along with a level tripod will help the telescope better predict the available bright stars and planets that are above the horizon. Remember to select alignment stars that are as far apart in the sky as possible. For best results make sure that the third alignment star does not lie in a straight line between the first two stars. This may result in a failed alignment. Dont worry about confusing planets for stars when selecting alignment objects. SkyAlign works with the four brightest planets (Venus, Jupiter, Saturn and Mars) as well as the Moon. In addition to the planets, the hand control has over 80 bright alignment stars to choose from (down to 2.5 magnitude). Rarely SkyAlign will not be able to determine what three alignment objects were centered. This sometime happens when a bright planet or the Moon passes near one of the brighter stars. In situations like these it is best to try to avoid aligning to either object if possible. Be sure to center the objects with the same final movements as the direction of the GoTo Approach. For example, if the scope normally finishes a GoTo with the front of the scope moving right and up, you should center all three alignment objects in the eyepiece using the right and up arrow buttons (the up/down arrows reverse at slew rates of 6 or lower). Approaching the star from this direction when looking through the eyepiece will eliminate much of the backlash between the gears and assure the most accurate alignment possible.

One-Star Align One-Star Align requires you to input all the same information as you would for the Two-Star Align procedure (see owner's manual). However, instead of slewing to two alignment stars for centering and alignment, the NexStar uses only one star to model the sky based on the information given. This will allow you to roughly slew to the coordinates of bright objects like the moon and planets and gives the NexStar the information needed to track objects in altazimuth in any part of the sky. One-Star Align is not meant to be used to accurately locate small or faint deep-sky objects or to track objects accurately for photography. To use One-Star Align: 1. 2. 3. 4. Select One-Star Align from the alignment options. Press ENTER to accept the time/site information displayed on the display, or press UNDO to enter new information. The SELECT STAR 1 message will appear in the top row of the display. Use the Up and Down scroll keys (10) to select the star you wish to use for the first alignment star. Press ENTER. NexStar then asks you to center in the eyepiece the alignment star you selected. Use the direction arrow buttons to slew the telescope to the alignment star and carefully center the star in the finderscope. Press ENTER when centered. Then, center the star in the eyepiece and press ALIGN. Once in position, the NexStar will model the sky based on this information and display Align Successful.
Note: Once a One-Star Alignment has been done, you can use the Re-alignment feature (later in this section ) to improve your telescopes pointing accuracy.
Solar System Align 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 the telescope for night time 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. 2. Select Solar System Align from the alignment options. Press ENTER to accept the time/site information displayed on the display, or press UNDO to enter new information.
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. NexStar then asks you to center in the eyepiece the alignment object you selected. Use the direction arrow buttons to slew the telescope to the alignment object and carefully center it in the finderscope. Press ENTER when centered. Then, center the object in the eyepiece and press ALIGN.
Once in position, the NexStar will model the sky based on this information and display Align Successful. Tips for Using Solar System Align For safety purposes, the Sun will not be displayed in any of the hand controls 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: Press the UNDO button until the display reads NexStar SE Press the MENU button and use the Up and Down keys to select the Utilities menu. Press ENTER. Use the UP and Down keys to select Sun Menu and press ENTER. Press ENTER again to allow the Sun to appear on the hand control display.

1. 2. 3. 4.

The Sun can be removed from the display by using the same procedure as above. To improve the telescope pointing accuracy, you can use the Re-Align feature as described in your owner's manual.
Constellation Tour In addition to the Tour Mode, the NexStar telescope has a Constellation Tour that allows the user to take a tour of all the best objects within a particular constellation. Selecting Constellation from the LIST menu will display all the constellation names that are above the user defined horizon (filter limits). Once a constellation is selected, you can choose from any of the database object catalogs to produce a list of all the available objects in that constellation.
To see information and data about the displayed object, press the INFO key. To slew to the object displayed, press ENTER. To see the next tour object, press the Up key.

Sun Menu

For safety purposes the Sun will not be displayed as a database object unless it is first enabled. The enable the Sun, go to the Sun Menu and press ENTER. The Sun will now be displayed in the Planets catalog as can be used as an alignment object when using the Solar System Alignment method. To remove the Sun from displaying on the hand control, once again select the Sun Menu from the Utilities Menu and press ENTER.

Scrolling Menu

This menus allows you to change the rate of speed that the text scrolls across the hand control display. Press the Up (number 6) button to increase the speed of the text. Press the Down (number 9) button to decrease the speed of the text.
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NexStar Communication Protocol
This document describes the serial commands supported by the Celestron NexStar hand control. This information applies to the NexStar GPS, NexStar GPS-SA, NexStar iSeries, NexStar SE Series, NexStar GT, CPC, SLT, AdvancedGT, and CGE mounts. Communication to the hand control is 9600 bits/sec, no parity and one stop bit via the RS-232 port on the base of the hand control. Note: the GT hand control prior to version 104.0 should be treated as version 1.2 in the tables below. Version 104.0 should be treated as version 4.03.

Get Position Commands

The following commands retrieve the position of the telescope in either RA/DEC or AZM-ALT coordinates. The position is returned as a hexadecimal value that represents the fraction of a revolution around the axis. Two examples are given below: If the Get RA/DEC command returns 34AB,12CE then the DEC value is 12CE in hexadecimal. As a percentage of a revolution, this is 4814/65536 = 0.07346. To calculate degrees, simply multiply by 360, giving a value of 26.4441 degrees. If the precise GET AZM-ALT command returns 12AB0500,40000500 then the AZM value is 12AB0500 in hexadecimal. As a percentage of a revolution, this is 313197824/4294967296 = 0.0729 or 26.252 degrees.
The standard commands offer a precision of 1/65536 * 360 * 60 * 60 = about 19.8 arcseconds per unit while the precise commands offer a precision of 1/16777216 * 360 * 60 * 60 = about 0.08 arcseconds per unit (only the upper 24 bits are used). Note: if the telescope has not been aligned, the RA/DEC values will not be meaningful and the AZM-ALT values will be relative to where the telescope was powered on. After alignment, RA/DEC values will reflect the actual sky, azimuth will be indexed to North equals 0 and altitude will be indexed with 0 equal to the orientation where the optical tube is perpendicular to the azimuth axis. Command Function Get Get Get Get RA/DEC precise RA/DEC AZM-ALT precise AZM-ALT PC Command E e Z z Hand Control Response 34AB,12CE# 34AB0500,12CE0500# 12AB,4000# 12AB0500,40000500# Applies to Versions 1.2+ 1.6+ 1.2+ 2.2+

GOTO Commands

The following commands direct the telescope to GOTO a specified RA/DEC or AZM-ALT position. As with the Get Position commands, the values are in hexadecimal and represent the fraction of a rotation around the axis. Note: GOTO RA/DEC commands will not work unless the telescope is aligned. Command Function PC Command Hand Control Response # # # Applies to Versions 1.2+ 1.6+ 1.2+
GOTO RA/DEC GOTO precise RA/DEC GOTO AZM-ALT
R34AB,12CE r34AB0500,12CE0500 B12AB,4000

GOTO precise AZM-ALT

b12AB0500,40000500
To Sync to an object via serial commands, the user should center a known object in an eyepiece. Then the Sync serial command should be sent, using the celestial coordinates (RA and DEC) for that object. This causes future GOTO or Get Position commands to use coordinates relative to the Syncd position, improving pointing accuracy to nearby objects. (we probably don't need to mention "from the planetarium package" since it also improves pointing accuracy if they GoTo objects via the hand control.) The format for the RA/DEC positions in the Sync command is identical to the GOTO RA/Dec command. Command Function PC Command Hand Control Response # # Applies to Versions 4.10+ 4.10+
Sync RA/DEC Sync precise RA/DEC
S34AB,12CE s34AB0500,12CE0500

Tracking Commands

The following commands retrieve or set the tracking mode. Depending on the mount type, following tracking modes are available: 0 = Off 1 = Alt/Az 2 = EQ North 3 = EQ South Note: On the CGE and Advanced GT hand control versions 3.01 through 3.04 the value for EQ North is 1 and EQ South is 2. This has been corrected to match the other models in current hand control versions. Command Function Get Tracking Mode Set Tracking Mode PC Command t T & chr(mode) Hand Control Response chr(mode) & # # Applies to Versions 2.3+ 1.6+

Slewing Commands

The following commands allow you to slew (move) the telescope at fixed or variable rates. For variable rates, multiply the desired rate by 4 and then separate it into a high and low byte. For example if the desired tracking rate is 150 arcseconds/second, then: trackRateHigh = (150 * 4) \ 256 = 2, and trackRateLow = (150 * 4) mod 256 = 88 For fixed rates, simply use a value from 1-9 (or 0 to stop) to mimic the equivalent hand control rates. Note: in most configurations, issuing the slew commands will override (or conflict with) the tracking mode of the mount. Hence it is always best to disable tracking first using the Tracking Commands, issue the slew command, then re-enable tracking. The main exception to this is when tracking equatorially - the fixed rate slews at 1 or 2 will not override tracking. This can be useful to simulate autoguiding. Note: on GT models, the fixed rate slews at rate 9 move at 3 degrees per second instead of the maximum rate.

Command Function Variable rate Azm (or RA) slew in positive direction
PC Command P & chr(3) & chr(16) & chr(6) & chr(trackRateHigh) & chr(trackRateLow) & chr(0) & chr(0) P & chr(3) & chr(16) & chr(7) & chr(trackRateHigh) & chr(trackRateLow) & chr(0) & chr(0) P & chr(3) & chr(17) & chr(6) & chr(trackRateHigh) & chr(trackRateLow) & chr(0) & chr(0) P & chr(3) & chr(17) & chr(7) & chr(trackRateHigh) & chr(trackRateLow) & chr(0) & chr(0) P & chr(2) & chr(16) & chr(36) & chr(rate) & chr(0) & chr(0) & chr(0) P & chr(2) & chr(16) & chr(37) & chr(rate) & chr(0) & chr(0) & chr(0) P &

Hand Control Response #

Applies to Versions 1.6+
Variable rate Azm (or RA) slew in negative direction
Variable rate Alt (or Dec) slew in positive direction
Variable rate Alt (or Dec) slew in negative direction
Fixed rate Azm (or RA) slew in positive direction
Fixed rate Azm (or RA) slew in negative direction

Fixed rate Alt (or DEC)

slew in positive direction
Fixed rate ALT (or DEC) slew in negative direction
chr(2) & chr(17) & chr(36) & chr(rate) & chr(0) & chr(0) & chr(0) P & chr(2) & chr(17) & chr(37) & chr(rate) & chr(0) & chr(0) & chr(0)
Time/Location Commands (Hand Control)
The following commands set the time and location in the hand control. The format of the location commands is: ABCDEFGH, where: A is the number of degrees of latitude. B is the number of minutes of latitude. C is the number of seconds of latitude. D is 0 for north and 1 for south. E is the number of degrees of longitude. F is the number of minutes of longitude. G is the number of seconds of longitude. H is 0 for east and 1 for west. For example, to set the location to 1182017 W, 335041 N, you would send (note that latitude is before longitude): W & chr(33) & chr(50) & chr(41) & chr(0) & chr(118) & chr(20) & chr(17) & chr(1) The format of the time commands is: QRSTUVWX, where: Q is the hour (24 hour clock). R is the minutes. S is the seconds. T is the month. U is the day. V is the year (century assumed as 20). W is the offset from GMT for the time zone. Note: if zone is negative, use 256-zone. X is 1 to enable Daylight Savings and 0 for Standard Time. For example, to set the time to 3:26:00PM on April 6, 2005 in the Eastern time zone (-5 UTC: 256-5 = 251) you would send: H & chr(15) & chr(26) & chr(0) & chr(4) & chr(6) & chr(5) & chr(251) & chr(1) Note: All values are sent in binary format, not ASCII. Note: The Get commands do not retrieve the time and location from the GPS unit (if one is present). The time and location are retrieved from the hand control. You must first enter the View Time/Site menu to update the hand control time if you want the time from the GPS or, use the GPS Commands in the next section. Command Function PC Command Hand Control Applies to Versions

Get Location

Set Location

Get Time

W & chr(A) chr(B) chr(C) chr(D) chr(E) chr(F) chr(G) chr(H) h
Response chr(A) & chr(B) & chr(C) & chr(D) & chr(E) & chr(F) & chr(G) & chr(H) & # # & & & & & & & chr(Q) chr(R) chr(S) chr(T) chr(U) chr(V) chr(W) chr(X) # # & & & & & & & & & & & & & & &

Set Time

H & chr(Q) chr(R) chr(S) chr(T) chr(U) chr(V) chr(W) chr(X)

GPS Commands

The following table shows various commands that can be sent to a GPS unit. Note: all units of time are in UT. Command Function Is GPS Linked? X > 0 if linked, 0 if not linked PC Command P & chr(1) & chr(176) & chr(55) & chr(0) & chr(0) & chr(0) & chr(1) P & chr(1) & chr(176) & Hand Control Response chr(x) & # Applies to Versions 1.6+
Get Latitude ((x*65536)+(y*256)+z)/(2
chr(x) & chr(y) & chr(z) &
^24) is a fraction of a rotation. To convert to degrees, multiply by 360.
chr(1) chr(0) chr(0) chr(0) chr(3)

& & & &

Get Longitude ((x*65536)+(y*256)+z)/(2 ^24) is a fraction of a rotation. To convert to degrees, multiply by 360.
P & chr(1) & chr(176) & chr(2) & chr(0) & chr(0) & chr(0) & chr(3) P & chr(1) & chr(176) & chr(3) & chr(0) & chr(0) & chr(0) & chr(2) P & chr(1) & chr(176) & chr(4) & chr(0) & chr(0) & chr(0) & chr(2) P & chr(1) & chr(176) & chr(51) & chr(0) & chr(0) & chr(0) & chr(3)
chr(x) & chr(y) & chr(z) & #
Get Date x is month (1-12) y is day (1-31)
chr(x) & chr(y) & #
Get Year (x * 256) + y = year
Get Time x is the hours y is the minutes z is the seconds

RTC Commands

The following table shows various RTC commands on the CGE mount. Command Function Get Date x is month (1-12) y is day (1-31) PC Command P & chr(1) & chr(178) & chr(3) & chr(0) & chr(0) & chr(0) & Hand Control Response chr(x) & chr(y) & # Applies to Versions 1.6+
chr(2) Get Year (x * 256) + y = year P & chr(1) & chr(178) & chr(4) & chr(0) & chr(0) & chr(0) & chr(2) P & chr(1) & chr(178) & chr(51) & chr(0) & chr(0) & chr(0) & chr(3) P & chr(3) & chr(178) & chr(131) & chr(x) & chr(y) & chr(0) & chr(0) P & chr(3) & chr(178) & chr(132) & chr(x) & chr(y) & chr(0) & chr(0) P & chr(4) & chr(178) & chr(179) & chr(x) & chr(y) & chr(z) & chr(0) chr(x) & chr(y) & # 1.6+

Set Date x is month (1-12) y is day (1-31)
Set Year (x * 256) + y = year
Set Time x is the hours y is the minutes z is the seconds

Miscellaneous Commands

Command Function Get Version PC Command V Hand Control Response chr(major) & chr(minor) & # Applies to Versions 1.2+
Get Device Version Devices include: 16 = AZM/RA Motor 17 = ALT/DEC Motor 176 = GPS Unit 178 = RTC (CGE only)
P & chr(1) & chr(dev) & chr(254) & chr(0) & chr(0) & chr(0) & chr(2) m
chr(major) & chr(minor) & #
Get Model 1 = GPS Series 3 = i-Series 4 = i-Series SE 5 = CGE 6 = Advanced GT 7 = SLT 9 = CPC 10 = GT 11 = 4/5 SE 12 = 6/8 SE Echo - useful to check communication Is Alignment Complete? - align=1 if aligned and 0 if not Is GOTO in Progress? - Response is ASCII 0 or 1 Cancel GOTO

chr(model) & #

K & chr(x) J

chr(x) & #

chr(align) & # prog & #

Developer Notes Timeouts

If the hand control is sent a command that requires it to communicate with another device, then the hand control will make multiple attempts to get the message through in the event of communications problems. Examples include Get Position commands, GOTO in Progress commands, etc. Software drivers should be prepared to wait up to 3.5s (worst case scenario) for a hand control response. If serial commands are blindly sent without waiting for a response, then some commands may be dropped or the software driver could see responses that are for earlier commands.
Pass-through Commands with No Response
Commands that start with P are special pass-through commands that communicate with a specific telescope device. For instance, the Slew commands talk directly to the motor control. If a P command is sent but no response is returned (because the device is not there or the command is unknown or there was a communication problem) then one extra data byte is returned before the # terminating character and any returned data is garbage. This is done to give software drivers a flag that something went wrong so appropriate action can be taken. It is particularly useful if you want to check for the existence of a device: for instance, check the time from the GPS unit, and look for an error response. Software drivers should check for the # termination character and if it is a different character then the next character (hopefully #) should be consumed and any command-specific handling should be done.