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

Bi-monthly release with minor bug fixes and improvements

Bad guiding, how can I fix things?

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(I use PHD2 for now - is that guide image above from the new version of the internal guider? the smoothed-out graph is OK, but the actual individual guide pulses really need to be shown and not abstracted into a smooth curve like that)

Paolo, if it is really taking that long for Dec to respond to pulses, there is definitely something mechanical. The CEM70, properly adjusted, should have virtually zero backlash or stiction. The easiest adjustment is the mesh, that can be done without taking anything apart. Next easiest is belt tension. You will need to take the Dec housing cover off, and you should get the iOptron pdf showing how to make the adjustment on the CEM70. I'm sure it must be floating around the internet somewhere, or you can email support and wait for them to reply. The belt adjustment isn't very sophisticated - loosen the motor in its housing and use a screwdriver for leverage to push the motor against the belt and retighten, repeating until you get what iOptron says is the goal (usually "about 3mm deflection when you push on the belt with a finger").

I wouldn't even think about any more significant teardown/cleaning until you've got mesh and tension correct.
2 years 1 month ago #80887

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Yes and no :) that data is from the internal guider, but that image is from the analyze tab in Ekos.

I've gotta gather more and better data. I hope to be able to run more tests next week!
2 years 1 month ago #80898

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This is VERY interesting as recently I have basically the same issue as earlier in the fall all was great - over the past two nights I have gone through all mechanical aspects and can see no backlash and then last night I did and experiment:
I have my guide rate set for 1 in indi (EQ6 using Onstep - yeah I know, diff mount but bear with me) - I manually used EKOS controls to watch the dec guide operations - mammoth backlash to the south - PHD2 guide assistant showed the same and a straight line across the graph after north movement was fine...ok I say I must have lose gears....but before I rip it all apart I set my rate to 0.5 and and added 500 as the backlash - calibrated and did GA again - this time the deck backlash was so small there was no need for PHD2 compensation.....ok...lets try EKOS

I see that my dec is now jumpy - so crank DOWN backlash to a few low numbers to test - ending on 100 which is really normal....hours of good guiding after this
So my THEORY (since the 100 backlash cannot possibly correct what I saw in first stage with NO movement or massive 30 second backlash) is that there is sneaky little bug related to setting guide rate of 1 (regardless of what your mount FW has) - I FEEL like somehow the commands and or process actually does not fire the command or correct command + values if set for 1

Simply setting rate to 0.5 was like night and day - I ran out of sky before I set the BL back to 0 and see if I can repeat - anyway PAULO - check what you have set and try 0.5 or 0.25 if supported - I will be doing the same as I try to dig this out - My old setting SHOULD have just had not great guiding, not something that looks like 30 seconds backlash when all mechanical tests show good and instant operations - (therefore I have to suspect SW) - Give it a try and let me know!!
2 years 1 month ago #80922

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Update on my CEM70...I adjusted gear mesh and tightened the RA belt as it was a bit loose.  Guiding was a bit better, mostly in the 0.6-0.7" RMS range, though at times it did push 1.0 or so.

I did a longer run with RA and DEC unchecked in the guiding tab to look at the unguided mount performance.  Exposure time was 2s.  I opened the log file in PHDLogViewer, shown below.
 

I'm not thrilled by the +/- 10" periodic error, but the curve appears fairly smooth, so proper guiding parameters should be able to deal with it.  I'd like to train the mount PEC chip to handle the error but so far I haven't had any luck there.  Very interested to see what others get.

I'm beginning to think I've just had bad seeing conditions lately, along with a loose belt.
Last edit: 2 years 4 weeks ago by Casey Offord.
2 years 4 weeks ago #80966
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@Jamie: good point. I'll check the HC and EKOS settings for the guiding rates. I honestly have never checked the, I have no idea what the current value is.

@Casey: how did you find the procedure for the belt tightening? Easy? Were ioptron instructions good enough? I think I'll too have a look at the RA/DEC belts In the coming days.
2 years 4 weeks ago #80977

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