#iEXOS-100 RA slippage/binding #iEXOS-100


Jaimie Murdock
 

Hey everyone,
 
I've been using my iEXOS-100 reasonably successfully for about 9 months now. This week my RA axis started showing a lot more lash and associated guiding issues, so I looked at the adjustment video and tried to fix the worm mesh.
 
Unfortunately, I've spent ~6 hours on it at this point and am really in need of help - possibly even sending it in to ES? 
 
The mount is slipping along the RA axis, no matter if I let some lash into the mesh or put it almost bound. I can't even get a 5-second exposure without star trails! The dec axis is fine. The mount tracking is on, and each time I'd test, I examined the polar alignment to make sure I was within 30 arcsec. That degree of tolerance was doing well enough for me with guiding while imaging with 1-2 min subs.
 
One odd thing is that when I plate solve with the mount it is able to dial in the Dec axis perfectly, but the RA gets to about 200 arcsec accuracy, then is no longer able to move from there. That seems to indicate binding, but when I loosen the mesh to introduce some lash, it would do the same. I tried balancing east-heavy as well, with no impact to this.
 
Here is a video of the mount alternating between tracking and minor slew attempts to resolve the 200 arcsec issues: https://youtu.be/XRAa8IM51CI
 
The mesh had a very minor degree of lash at this point - better than preadjustment, but pre-adjustment I wasn't having issues with trails while tracking.
 
I'd really appreciate any feedback. I'm unsure if the noises the mount is making are normal. The tracking noises certainly seem to be the same and I haven't heard any terrible grinding noises or experienced the mount totally stopping.

Really excited to get back to imaging - our rainy season just ended here in New Mexico and clear skies are the norm.

Thank you,
Jaimie

--
Mount: ES PMC-8 iEXOS-100
Scope: William Optics ZenithStar 61II w/ WO UniGuide 32mm
Cameras: ZWO ASI533MC Pro, ZWO ASI120MM Mini (guide)
Software: KStars on Astroberry, DeepSkyStacker and Photoshop


Wes Mcdonald
 

Jaimie

Sure looks like things are turning.  

Not that you should, but did you update your firmware to the new 2A01.1?  Trying to figure out what has changed on your system.

Wes.


--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Jaimie Murdock
 

I’ve not updated the firmware yet - driver reports version 1A10B5. During the 3 month rainy season, I was only able to get out once every other week, so didn’t want to waste a night debugging the mount if anything went wrong. It’s next on my list after working out the lash issues.

I have had an issue where occasionally the INDI driver starts with the G11 instead of iEXOS-100. I double-triple-checked that wasn’t happening here.

However, I just fired it up to get the firmware version and noticed that the tracking was set to “Custom” rather than “Sidereal”, with RA at 38.75 arcsec/s, Dec at 0. Maybe that’s the cause of error… will test again when after dark.

--
Mount: ES PMC-8 iEXOS-100
Scope: William Optics ZenithStar 61II w/ UniGuide 32mm
Cameras: ZWO ASI533MC Pro, ZWO ASI120MM Mini
Software: KStars on Astroberry, DeepSkyStacker and Photoshop


Wes Mcdonald
 

Jaimie

Yes that is the problem.  For sure.  I did notice I thought your small pulley was running too fast in your video.  Star trails would absolutely be happening.

Also you should add to your signature that you are running asiair.

The reason I was asking about the firmware was to make sure you had not identified some issue with the new release.

Wes


--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Jaimie Murdock
 

To close the loop: the tracking rate was the issue.

One of the best parts about this hobby is that if you really understand what went wrong, there’s a mathematical explanation.

I was stuck at ~200 arcsec RA error in plate solving because of the rate. I was drifting ~22 arcsec/s faster than sidereal rotation. Given the following time 
- 4.8s plate solving
- 1.5s slew & settle
- 3s image acquisition
- 0.3s image download
Total: 9.6s, yielding 220.8 arcsec error.

Worm mesh is doing well. Some guiding issues tonight with an occasional breeze, but the mount is behaving at least as well as before.

Thanks for the help!

Jaimie

On Mon, Sep 13, 2021 at 12:44 PM Wes Mcdonald <wesmcd6@...> wrote:
Jaimie

Yes that is the problem.  For sure.  I did notice I thought your small pulley was running too fast in your video.  Star trails would absolutely be happening.

Also you should add to your signature that you are running asiair.

The reason I was asking about the firmware was to make sure you had not identified some issue with the new release.

Wes


--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


--
Mount: ES PMC-8 iEXOS-100
Scope: William Optics ZenithStar 61II w/ UniGuide 32mm
Cameras: Canon EOS 1100D (Rebel T3), QHY-5-III-462C
Software: KStars on Astroberry, DeepSkyStacker and Photoshop


Wes Mcdonald
 

Jaimie

Great.   Thanks for closing the loop on this.

In theory, most of what happens is explainable if the problem formulation is correct, observations are complete, and the right neuron fires.

Wes



--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired