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INDI Library v1.9.5 Released (08 Mar 2022)

Bi-monthly INDI Library released with new drivers and bug fixes.

Celestron CGX - Unexpected / Not-Understood Behavior

  • Posts: 6
  • Thank you received: 3
I recently migrated to a Celestron CGX from an Orion ATLAS EQ-G via EQMOD, and am struggling with understanding the Celestron CGX driver.
I believe I am using "indi_celestron_gps" version 3.2 interface 5 as selected when I choose "Celestron CGX" from the mount time.

1) There appears no way to connect directly to the mount - you MUST connect via the hand controller USB. This would appear to be a limitation imposed by Celestron, and no one has cracked the proprietary mount USB yet.

2) The mount appears to be implementing some kind of hard-coded backlash compensation - every GOTO, no matter how small, or in what direction, results in the mount slewing away from the current position, and re-approaching it from the lower left in both axes. I can not find any parameters to tune or disable this. In Kstars/Ekos, this is especially annoying on Capture & Solve -> Slew to Target mode, as it requires about 6.5 seconds to do this dance in order to "settle" for the next try, and this technique still fails to completely solve mount model problems that the EQ5-G had in small moves through backlash.

3) There appears to be no way to slew to a position and "STOP". Slew / GOTO always results in entering "TRACK" mode regardless of whether it is to to "TRACK, SLEW, or SYNC" in the "On Set" INDI dialog. This has made manual points (for example, in surveying my horizon for creation of a horizon mask) more intensive, as I always have to tell it to manually STOP tracking.

Is there a better resource for documentation / setup than here (which does not yet mention the CGX in supported mounts) indilib.org/devices/telescopes/celestron/celestron-nexstar.html
2 years 8 months ago #42817

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  • Posts: 554
  • Thank you received: 138
1) Correct, only the HC connection provides the mount Ra and Dec information. The internal AUX bus protocol only handles low level mount axis commands.

2) This is a feature of how Celestron manages backlash on slews. It isn't under INDI's control.

3) If the mount has tracking turned off on the HC then subsequent moves leave tracking off. Perhaps the INDI driver is turning tracking back on at the end of a slew. Is this really a problem for the setting a horizon use case? The position is only changing by an arc minute every 4 seconds.

That link needs updating, it's quite out of date.
2 years 8 months ago #42834

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It needs new screenshots and a better description all the new features + focusing part + credits ..etc. You have access to update the driver documentation.

Regarding #3, in INDI, "Slew" in ON_COORD_SET means GOTO and stop tracking. So if this is something that can be implemented by the Celestron driver, then it should be implemented to conform with this meaning. Perhaps it can be as simple as turning tracking off after the slew is complete.
Jasem Mutlaq
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2 years 8 months ago #42844

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I don't think that the mount will spontaneously start tracking after a slew if tracking was turned off before the slew. A log file showing the commands sent to the mount would help.

Updating the documentation is tricky, I didn't even know there was any and people who's talent is software may not also have a talent for documentation and web site design.
2 years 8 months ago #42848

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