NexStar Resource Site

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Firmware Versions on the CGEM/CGEM DX Series

Non-English Hand Control Owners - read this.  The
information below is for English-version hand controls.

CGEM scopes have two sets of processors. There are processors in the hand control (HC) and there are processors in the base of the scope in a section known as the motor control (MC). 

There have been two versions of hand control available for the CGEM/CGEM DX:

  • Hand control version 4.X.  This hand control can be updated by the owner.  Read this for step by step instructions on upgrading the firmware.
  • The NexStar+ hand control.  This hand control can be updated by the owner and began shipping with new CGEM/CGEM DX scopes in January 2012.  It is also available for purchase since February 2012.  Read this for info on this new hand control and this for step by step instructions on upgrading the firmware.

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NexStar+ Hand Control

Celestron has posted an official document detailing all firmware versions for the NexStar+ hand control:
Check back periodically for updates.

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Version 4 Hand Control
(firmware files are named GEM)

  • 4.21 - Fixed bugs related to tandem operation (OTA orientation), Meridian Mode and land objects.
  • 4.20 - Fixed a problem with a runaway slow slew if a GoTo is too near the meridian flip point.  No Response errors now give a "Press UNDO to continue" option.  For mounts with a GPS module in use, changed the messages displayed to clarify when the GPS was still attempting a link and when it was successful.  Fixed and error when syncing on stars in southern hemisphere via the RS-232 sync command (for example, from a planetarium program running on a laptop).
  • 4.19 - Adjust communication protocol to assist MCupdate.  Added "Custom Rate 9": the ability to set the maximum slew rate during a GoTo (requires MC version 6.12 or higher).  Fixed an error in the GoTo RA-Dec menu item.  Hand Control now reports immediately if the are communication ("No Response") difficulties at start up.
  • 4.16 - Corrects alignment system errors for use in the Southern Hemisphere.  Fixed error when using SAO stars (selected from the STAR button) as alignment objects.
  • 4.15 - Original version for the CGEM Series.  This version is largely unusable in the Southern Hemisphere.

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MC Versions

  • 6.50 - Improves guiding in Declination solving problems caused by mechanical backlash and motor cogging.  Improved anti-backlash compensation.  Numerous improvements matching those found in the AVX mount.
  • 6.17 - First version supporting the CGEM DX mount.  Re-tuned motor control feedback loop and adjusted motor acceleration to better handle heavy payloads.  Fixed problem with sudden motor deceleration for high values of "Custom Rate 9".   The final GoTo approach is now faster and quieter. Fixed error in GoTos near celestial equator.
  • 6.12 - Support for "Custom Rate 9" (introduced in HC version 4.19 - see above).  Added new "Aux" command to support better autoguiding via RS-232 communication via the port on the bottom of the hand control.  Fixed an error that prevented some user settings from being restored when the scope is powered up.
  • 6.08 - Corrects errors with recording PEC and with GoTo accuracy after canceling PEC training or using PECTool.
  • 6.06 - Original version on the CGEM Series.

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Determining Versions

Use the Version option on the Utility menu.

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Michael Swanson
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