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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Meridian Flip Spins OTA

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My first Meridian Flip went pretty wrong last night and I'd like to ask whether I'm doing anything obviously wrong in EKOS settings.

I set up to capture the Veil Nebula which was almost overhead at the time. The OTA slewed so that its axis was pointing due west and the OTA just about vertical. I took some test shots using a laptop connected over nomachine and all seemed well. I retired indoors to create a sequence of 60x20s subs from a desktop PC & nomachine. I ran the capture and a few minutes later saw that capture had paused after 8 subs and the message box said MF was underway. As I hadn't seen this working yet I zipped outside to watch it. 

What I saw was the OTA/mount was stationary, the OTA was pointed vertically down, axis pointing west and the USB cables to the OTA (for camera/EAF/dew heater) were wrapped tightly around the mount. I immediately powered everything off and to untangle the cables I had to rotate the OTA 540 degrees. Looking at the control cabling between the two halves of the mount its also possible that the whole mount had rotated from west through east and back to west. Fortunately as the ZWO is small it seems the OTA/Camera did not strike the mount.

I don't have any logs as they weren't enabled at the time, but is there anything obvious that anyone can see I'm doing wrong please ?

The equipment is: Ubuntu 20LTS with kstars-bleeding / Explore Scientific iEXOS-100 mount / ZS 61 with field flattener / ZWO EAF / ZWO 178MC / no guiding.

I will try to simulate the same during the day today with log capture on and watch whether the same happens.
2 years 4 months ago #77068

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Thank you for the report. Please note that Ekos does not actually control the meridian flip per se. It just issues a GOTO to the same position the mount is currently tracking. The mount then performs the meridian flip. You can test this manually. Allow the mount the track pass the meridian for a few degrees, then at the same point, right click and issue a GOTO there. The mount should flip. Some mounts have flip configuration in the handset that you can alter..etc.
2 years 4 months ago #77070

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Replied by Damian on topic Meridian Flip Spins OTA

Thanks for your quick reply and explanation Jasem.

I tested the goto command after a test target passed the meridian and it worked as expected.
I chose another target and set auto-flip if passing 0 degrees and that worked as expected.
I created a imaging session which ran and after it completed the auto-flip worked as expected.
It seems when I watch it then it works correctly.

I'll keep an eye on it. Now that I understand that the hour angle tells me when it will flip I can watch it for the next few targets.
2 years 4 months ago #77073

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Replied by Damian on topic Meridian Flip Spins OTA

OK It happened again last night.

I set an alarm for 2:30am when the target passes the meridian but didn't wake, so missed it. When I went to the mount at 3:45 it was spun and the cables on both axes were wrapped around their shafts. Pictures below.
What I can see though is that both axes went beyond their end stops. Could it be an incorrect setting in the mount setup that allows this ?
If anyone can post what should be set on this I'd be grateful.
I also remember there are a lot of options in EKOS setup around which way is up/down etc. Could I have these set up wrongly and could cause this ?
Any help gratefully accepted.   



021-11-05T03:45:26 CCD capture aborted
2021-11-05T03:45:26 Post-flip alignment failed.
2021-11-05T03:45:13 Post-flip alignment failed. Retrying...
2021-11-05T03:45:00 Post-flip alignment failed. Retrying...
2021-11-05T03:42:56 Performing post flip re-alignment...
2021-11-05T03:42:56 Telescope completed the meridian flip.
2021-11-05T03:41:38 Received image 6 out of 50.
2021-11-05T03:41:38 Download Time: 0.71 s, New Download Time Estimate: 0.74 s.
2021-11-05T03:41:04 Capturing 30.000-second image...
2021-11-05T03:41:04 Dither complete.
2021-11-05T03:41:04 Dithering succeeded.
2021-11-05T03:41:01 Dithering...
2021-11-05T03:41:01 Received image 5 out of 50.
2021-11-05T03:41:01 Download Time: 0.72 s, New Download Time Estimate: 0.74 s.
2021-11-05T03:40:27 Capturing 30.000-second image...
Last edit: 2 years 4 months ago by Damian.
2 years 4 months ago #77263
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Replied by AstroMuni on topic Meridian Flip Spins OTA

Hi Damian,
I find it useful to get Kstars to display the Meridian as you can quickly spot if your object is likely to be subject to a MF.
2 years 4 months ago #77265

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Replied by Damian on topic Meridian Flip Spins OTA

Hi Astromuni,
Yes it's a good idea. Jasem mentioned it before and I did add it.
Problem is I fell asleep !
2 years 4 months ago #77266

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Replied by AstroMuni on topic Meridian Flip Spins OTA

Just a thought here....attempt to do the MF by hand and see if cables get tangled up at some point. Once even a single cable gets snagged it might end up dragging the scope in wrong direction.
2 years 4 months ago #77267

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Replied by Damian on topic Meridian Flip Spins OTA

Thanks for the suggestion.
In the 3rd post in the thread I mentioned that I did test it by hand and it completely behaved then.
As I untangled everything I could see that both axes turned 1.5 complete turns. Very strange.
2 years 4 months ago #77268

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Replied by Damian on topic Meridian Flip Spins OTA

Testing during daytime always succeeds but it does not include plate solving, which in the log I posted above was what was failing. I'll need to test at night when there's even a possibility of a star - poor weather outlook for now.

I think I read in the docs for EKOS that MF needed to know which side of the mount the OTA was on. Mine apparently does not, although the OTA is sent to the correct side of the mount when I slew to an object in Kstars. Just wondered whether this might be a contributing factor. Is this showing in EKOS for anyone else using the iEXOS-100 mount please ?

  
Last edit: 2 years 4 months ago by Damian.
2 years 4 months ago #77283
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Replied by Damian on topic Meridian Flip Spins OTA

Had a chance to debug this under a starry sky.
After a first goto / track/ image capture, select park and it the mount keeps going in whichever side of the pier/tripod it's on, trying to twist the cables again. Had to power down to stop it.
For now I'm not using MF and getting some images manually.
Will raise it on the indilib driver bug area.

Is anyone successfully using a PMC-8 mount with EKOS & MF, who'd be willing to compare configurations please ?
2 years 4 months ago #77342

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Replied by Damian on topic Meridian Flip Spins OTA

After a conversation on the forums for the PMC-8 mounts, the situation is:

it looks like my choices are:
1) Contact the INDI PMC-8 driver developer and try to come up with a fix for MF.
2) Switch to Windows 10 and start the whole software selection and integration thing.
3) Keep Kstars/EKOS/INDI and replace the mount with one with a more fully developed driver.
4) Just live with it and don't do automatic MF :)

Is it possible to contact the author of the INDI driver for PMC-8 ? @Jasem I think you're down as the author but do you work with Chris on that please ?
I'd be happy to put this mount at your disposal to investigate the issue. I appreciate that verbose logs would be the first step and I'll collect those the next time we have the hint of a star in the sky.
2 years 4 months ago #77409

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Please open an issue at INDI Github and let's see if we can follow up there. Michael Fulbright, Thomas Olson, and Karl Rees developed this driver.
2 years 4 months ago #77414

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