Wanted to add some additional information to this thread. More specifically about the command used to SYNC an Astrophysics mount.
In the indi_lx200ap driver there are two options for how SYNC commands are handled. :CM# and :CMR#. This is a very important distinction, according to the folks at AP. The preferred method of SYNC commands to their mounts is RE-CAL, which is :CMR#.
Here is info directly from their public documentation on the mount:
www.astro-physics.com/tech_support/mounts/protocol-G.pdf
Command: :CM#
Response: “Coordinates matched. #”
(there are 5 spaces between “Coordinates” and “matched”, and 8 trailing spaces before the “#”, the total response length is 32 character plus the “#”.
Calibrate mount (
Sync). Current Right Ascension and Declination become the commanded Right Ascension and Declination respectively if in RA-DEC mode. If in ALT-AZ mode, then the commanded Altitude and Azimuth become the current. This command
assumes that the mount has been manually positioned on the proper pier side for the calibration object. This command is ignored if slewing is in progress. This command
should be used for initial calibration. It
should not be used after the mount has been tracking unless it is known that it has not tracked across the meridian. Please refer to the most recent version of the Keypad Manual for a complete discussion of how Sync and Re-Cal should be used.
Command: :CMR#
Response: “Coordinates matched. #”
(there are 5 spaces between “Coordinates” and “matched”, and 8 trailing spaces before the “#”, the total response length is 32 character plus the “#”.
Re-calibrate (
Re-Cal) mount. This command performs a function very similar to the :CM# command with one exception. It
does not assume that the user has manually positioned the mount on the proper pier side for the object in view. It assumes that the pier side has not changed since the most recent :CM# or :MS# commands. It a
llows re-calibration on known coordinates even if the mount has tracked across the meridian.
With all of this said, the provided APCC and Astro Physics ASCOM drivers convert all SYNC commands sent to them into RE-CAL commands. SYNC can be used in the event that you are positive that the scope and the object are on opposite sides of the meridian, and only when you are doing your initial calibration. After that you should only send :CMR# (Re-Cal) commands to the mount.
Here is the caution from the AP hand controller documentation:
www.astro-physics.com/tech_support/mount...ad/keypad-manual.pdf
Page 54-57 talks about SYNC vs RE-CAL.
CAUTION: It is important to note that external software programs may not make the same distinction between the 2 terms, so be careful when syncing or re-calibrating (or whatever they call it) with other programs. For safety sake you may want to treat any similar command in external software like a Sync command and use it only with the object and telescope on opposite sides of the meridian.