Argh - autofocus gone wrong. - Forums

Topic starter

Feb 13, 2023

I set up last night with my SD81S, SXD2 mount and ASIair Plus.

M81 was directly overhead, I ran the autofocus facility, set guiding off, and started an Autorun routine consisting of 60x180". Autofocus was set to run every hour.

The first hour seemed to go fine

But then the autofocus routine ran...and failed, giving images like this...

The autofocus tried again an hour later, but then guiding failed too (I quite like this one!).

Finally, the mount didn't even return to the home position.

Autorun_Log_2023-02-12_221439.txt

The log is above - any help, gratefully received!

Engaging

Marc-Antonio Fischer

Feb 13, 2023

Most AF problems are related to backlash problems. Is the focuser tightly mounted? Are the focuslock screws open? Try you focuser during daytime with full equipment load. Go to a certant focus position, remember or mark the focuser tube, go at least 200-1000 steps inwards/outwards (depents on focuser model) and then go the same amount backwards. It should be on the excat same position if not there is a backlash problem. Its a lot of try and error until the backlash is finaly right. Had many problems with cheap focuser. Ive got a RC and when its poiting directy in the sky the gravity drags the camera focuser down and the backlash is stronger…. its really annoying

Piers Palmer

Topic starter

Feb 13, 2023

Thanks - I'll try that and I did wonder if it was because, pointing straight up, the weight might be causing an issue.

I think I had sorted the backlash, but I'm going to check!

Piers Palmer

Topic starter

Feb 13, 2023

Well the backlash seems fine - not sure what's going on there yet, but the guiding issue is sorted….I need a half pillar!

Marc-Antonio Fischer

Feb 13, 2023

Piers Palmer:
Thanks - I'll try that and I did wonder if it was because, pointing straight up, the weight might be causing an issue.

I think I had sorted the backlash, but I'm going to check!

Yes i think thats your main problem, because Ive got it too. Damn gravity 😂 you can try do focus on a other point in the sky were the telskop is not poiting exactly in the sky. But not a long term solition.... new focuser i think it is. You got barrings or tooth ?

Marc-Antonio Fischer

Feb 13, 2023

Do you use offaxis guding? That would be the reason too that the guding failed when its aslso out of focus

Piers Palmer

Topic starter

Feb 13, 2023

Thanks Mark - the focuser is Vixen's standard rack and pinion. It's not high tech but it is strong and robust. What I don't quite get is how the autofocus routine at the 1hr mark, started with a star size of 3.1 and then went from 13.9, down to 3.1 then back up to 10.8. Why would the software do that and give up? That would suggest to me that the weight wasn't an issue but it seems odd that it's worked fine before now.

No OAG for me, just a normal guide scope. I think I'd hit the tripod legs though so that one is easily explained!

Marc-Antonio Fischer

Feb 13, 2023

These HRF values seem fine to me. They fit the parabolic pattern. Main problem i guess is driving the focuser back to the lowest value at 3.1 from 10.8.. and this is most likely backlash… but you said you fixed it. Another tip. AF every hour is way too much imo. After a flip i enouth. At least with my equipment…

Piers Palmer

Topic starter

Feb 13, 2023

You make a good point - this is the first time I've ever set it up to focus every hour…and look what happens!

I'll have a play with the backlash again this afternoon and have another go tonight with an autorun routine.

Well Written

Marc-Antonio Fischer

Feb 13, 2023

Piers Palmer:
You make a good point - this is the first time I've ever set it up to focus every hour...and look what happens!

I'll have a play with the backlash again this afternoon and have another go tonight with an autorun routine.

Good luck my friend. Never surrender