Firmware Versions on the Advanced Series with
Non-English Hand Control Owners - read
information below is for English-version hand controls.
Celestron AS-GT 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). The MC firmware can be updated by
the owner (read
There have been three versions of hand control available for the AS-GT:
control 3.03 and 3.04. Hand controls prior to version 4 can NOT be updated.
- Hand control version 4.X. This hand control can be updated by the
owner and was available for purchase from January 2006 through summer 2012.
for info on purchasing the upgradeable hand control and
for step by step instructions on upgrading the firmware.
- The NexStar+ hand control. This hand control can be updated by the
owner and is available for purchase since February 2012. Read
for info on this new hand control and
for step by step instructions on upgrading the firmware.
For additional details about features on newer versions, check the
Manuals section of this web site.
NexStar+ Hand Control
Celestron has posted an official document detailing all firmware versions
for the NexStar+ hand control:
Check back periodically for updates.
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 - Added "Custom Rate 9": the ability to set the maximum slew rate
during a GoTo (requires motor control version 5.20 or higher). 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. Fixed an
error in the GoTo RA-Dec menu item. Hand Control now reports
immediately if the are communication ("No Response") difficulties at start
- 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 - Introduced with the CGEM, this version includes several changes.
All-Star Polar Alignment (ability to perform polar alignment on any star,
not just Polaris and Sigma Octanis) and tandem support (ability to turn the
RA axis 90 degrees and mount multiple optical tubes side-by-side) are two
new features. The hand control now uses precession to calculate
current coordinates rather than using static J2000 coordinates. After
polar alignment it is no longer necessary to repeat the star alignment.
User is now prompted automatically for the time during alignment if a GPS
module is not in use. Read the manual for the CGEM (found in the
Manuals section of this web
site) for details on how this all operates. NOTE: This version is
largely unusable in the Southern Hemisphere.
- 4.13 - This version allows the motor control (MC) firmware to be upgraded
via the port on the bottom of the hand control.
- 4.12 - The most significant change in this version is variable brightness
control for the display and buttons - values are from 0 (off) to 8 (full
brightness). There is also a fix that reduces (but does not eliminate)
the chance that the display comes up blank the first time you power up, a
problem much more prevalent in cold weather. The fix on those occasions
when it does still come up blank remains the same - turn off the power, wait a
couple of seconds and turn on the power again. The Version menu item has
been changed - it now displays the mount model after displaying the HC and MC
- 4.10 - The most significant change in this version is Sync and multiple
mount calibration stars. Sync is available both via the hand control and
via PC software (TheSky, Starry Night, etc.). This provides very
accurate GoTo pointing in the area of the sky where the Sync is performed and
it allows the PC software to match with the actual position the scope is
pointed to. Multiple mount calibration stars take the place of the
previous use of one calibration star for determining cone error and the Dec
switch/index mark offset resulting in much improved pointing accuracy.
Other new features: a display of the polar alignment error, Solar System
Align routine, the Sun is now available as a GoTo and alignment object, and
"RA" and "Dec" are used in most places in the menus rather than "Alt" and
- 4.0 - The most significant new feature of this version is that it is
user-upgradeable. Other changes from previous versions are simply minor
Non-upgradeable Hand Control
- 3.04 - The differences between this
and 3.03 are unknown.
- 3.03 - Original version on the AS-GT mount.
- 5.20 - Support for "Custom Rate 9": the ability to set the maximum slew
rate during a GoTo (requires hand control version 4.20 or higher). The
final GoTo approach is now faster and quieter.
- 5.16 - Corrects problems in RA Limits (previously named Slew Limits) and
improves precision of RA Limits to 1 degree (improved precision only
available when using hand control version 4.16 or higher).
- 5.14 - Corrects a potential problem with the cordwrap prevention feature.
Re-enables the RA Slew Limits.
- 5.07 - An official version. Minor changes - rate 1 is now 50% of
sidereal while rate 2 is 100% of sidereal. This makes manual guiding
- 5.06 - First official version available for download from Celestron. Improved
anti-backlash, fixed runaway slews during normal use and when when
autoguiding, general improvements to autoguiding, fixed occasional slow motion
slews that never seem to reach their destination, improved sidereal tracking
- 5.04 - Original version on the AS-GT mount.
Use the Version option on the Utility menu.