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PC Control of NexStar Telescopes

General Info

It is first important to understand that there are currently seven different NexStar hand controls on the market.  In order of their introduction: 

  • NexStar 5/8
  • Original NexStar GT (60/80/114/4)
  • NexStar GPS
  • New NexStar GT (introduced in December 2001)
  • Hand control version 2.2 and 2.3 for the the NexStar 5i/8i/8i Special Edition and NexStar GPS
  • CGE Series (current CGE scopes ship with hand control version 4)
  • AS-GT Series (current CGE scopes ship with hand control version 4)
  • Hand control version 4 - introduced with the CPC and compatible with the NexStar GPS, CPC, LCM, SE, SLT, GT, "i" series, CGE, CGE Pro, AS-GT, CGEM and StarSeeker

I provide more details about each of these hand control models on the last half of this page.

Additional Info

Programs Compatible with NexStar, CGE, CGE Pro, CGEM and AS-GT Scopes
Problems with PC to Scope Communications
Problems with PDA to Scope Communications
Hand Control RS-232 Port Cable
PC Port Cable
Diagram by Larry McNish Depicting NexStar Cable/Port Connections
NexRemote -  Software to Replace the Hand Control with a PC
Programming for NexStar Controlled Telescopes - Documentation and Examples

All of these scopes are connected to a PC or PDA via the RS-232 port on the bottom of the hand control (HC).  For more information about the various ports and connectors on your scope, visit the Odds and Ends section of this web site.  The correct cable is described in the link "Hand Control RS-232 Port Cable" above.  

If your PC does not have a serial port (very common with today's laptop/notebook computers) you will also need either an RS-232 port PC Card ($40 to $100) or a USB to serial adapter ($30 to $40).  Note that many people have problems with the USB adapters so the PC Card is a better solution if your laptop has a PC Card slot.  Most computer stores stock the USB to serial adapters but the PC Card can be hard to find in a local store.  Click here for Google results for RS-232 PC Cards.  The newest laptops now have an ExpressCard slot rather than PC Card slot.  Click here for Google results for RS-232 ExpressCards. 

PDAs (Palm Pilot, Pocket PC) require a serial "sync" cable or a serial port CF card which is used to connect to the Hand Control RS-232 Port Cable.  When using a CF card, the standard hand control RS-232 port cable is used.  When using a serial "sync" cable, you will need a null modem and gender changer to use the hand control RS-232 port cable or a custom cable.  Details of these cables are explained in the link "Hand Control RS-232 Port Cable" above.

Be sure to check out Larry McNish's diagram linked above.

Most of the information you find here is the result of my work on NexStar Observer List, a PC control program for all models of NexStar scopes.  You can learn more and download your free copy here.

Hand Control Version 4
Hand control version 4
is compatible with the CPC, LCM, NexStar GPS, NexStar 5i/8i/8i Special Edition, NexStar SE, NexStar SLT, NexStar GT, StarSeeker, CGE, CGE Pro, CGEM and AS-GT scopes.  The command set for this and most other versions of NexStar hand controls can be found in the link "Programming for NexStar Controlled Telescopes - Documentation and Examples" above.  Any program compatible with the NexStar GPS is basically compatible with this hand control, regardless which telescope you use it with, so if the setting for your particular scope doesn't work correctly, try NexStar GPS.

NexStar GPS
The NexStar 8/9.25/11 GPS control commands are detailed in a document from Celestron found in the link "Programming for NexStar Controlled Telescopes - Documentation and Examples" above.  The control commands are quite similar to commands for the Celestron Ultima 2000 (U2K).  Some telescope control programs that work with the U2K will work with the GPS, try that selection if a setting for the NexStar GPS is not available.

NexStar GT
The newer (version 101.0 - see Firmware Versions on this web site) NexStar GT hand control is capable of interfacing with PC based programs as documented in the latest NexStar GT manuals.   However, the NexStar 4 GT manual does not document this.  If you own a NexStar 4 GT, you might want to download the new 60/80/114/130 manual from the Manual section of this web site.  The GT control commands are detailed in a document from Celestron found in the link "Programming for NexStar Controlled Telescopes - Documentation and Examples" above - it is the same basic command set as the NexStar GPS.  If a programs doesn't have a setting for NexStar GT or if it doesn't work, try the NexStar GPS setting.

NexStar 5i/8i/8i Special Edition
The computerized hand controls for the NexStar 5i/8i/8i Special Edition (sometimes called the "iComp" hand control) are direct descendants of the GPS hand control and share the same command set as detailed in a document from Celestron found in the link "Programming for NexStar Controlled Telescopes - Documentation and Examples" above.  If a programs doesn't have a setting for NexStar 5i/8i use the NexStar GPS setting.

CGE and Advanced Series with GoTo
The CGE and AS-GT control commands are detailed in a document from Celestron found in the link "Programming for NexStar Controlled Telescopes - Documentation and Examples" above.  If a programs doesn't have a setting for CGE or Advanced Series, use the NexStar GPS setting.

NexStar 5/8
The control commands for the original NexStar 5/8 (not the 5i/8i) are documented in their manual.  It should noted that some, if not all, of the N5/8 hand controls exhibit a problem where occasionally they do not reply back to the PC after they finish slewing.  If a PC control program does not take this into account, it might wait forever for the slew to finish.  It is worth noting here that the original NexStar 5/8 is the only NexStar mount that is incompatible with the new version 4 hand control.

Original NexStar GT
The original NexStar GT hand control (the hand control for NexStar 60/80/114/4 scopes made prior to January 2002 and all Tasco StarGuide scopes) is capable of interfacing with PC based programs; all required commands are documented in the "Original GT Model Control Commands" link found above.  But there are some problems (explained in the link above) that make it less than enticing for commercial developers and so most software does not support the original GT hand control.  If you have a NexStar scope, you should consider purchasing a version 4 hand control.


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