Ekos guide calibration help

[RugbyRene]

Hi all,

I have a question about guiding and guide calibration.  So here’s my problem.

During an imaging session, I will go through guide calibration, start guiding and have a pretty good night (RMS - 0.5 to 0.7). On other nights I will use the exact same set-up, do a guide calibration again, only this time the dec and ra plot graphs will fly wildly off the chart and I have to stop the session as I can’t recover it. Sometimes this will happen during the same session if I slew to another target and do calibration again (should I be doing this?).

My set-up doesn’t change from night to night. My polar alignment is within 7 arc sec. My settings don’t change. My calibration pulse is set to 500. Not sure if this is the correct value but I read on this forum somewhere that’s the value I should use.

Can I re-use a previous nights calibration say from a week ago when I know everything was working? Should I be calibrating when I set-up again? Is the calibration plot meant to be orthogonal? The one last night wasn’t. It was straight up and down. What would cause this?

My mount is a SW AZEQ6GT. When it works I all works, I get really good guiding.

I did read on this forum to ensure my guide calibration has been done properly but it was never explained what “properly” was. So any advice would be appreciated.

Thanks in advance. I know there’s a lot to unpack but this is the last piece of the puzzle in getting my imaging sessions to run error free.

Rene

[alacant]

26 minutes ago, RugbyRene said:

Can I re-use a previous nights calibration say from a week ago

Yes, absolutely. Do it. Get a calibration which works and reuse it.

There is a checkbox in the guiding options to store the calibration.

I'd recommend using the latest SEP multistar which will help minimise your rms vaues further [1].

We cannot however advise on guide pulse length for calibration since we do not know which guide camera nor guide telescope being used, but if it's working with what you have set, stick with it.

Cheers

[1] but remember to look at your images, not numbers on a graph!

[michael8554]

13 hours ago, RugbyRene said:

My set-up doesn’t change from night to night.

Only need to recalibrate if the guidescope or cam has rotated since the last Cal.

Assuming you have a setup that feeds Dec position to the guide software, and that it uses that to adjust the RA rate to the changes in Dec.

PHD2 does that, but if your guide software doesn't, you will need to Cal on every new target.

13 hours ago, RugbyRene said:

Is the calibration plot meant to be orthogonal? The one last night wasn’t.

Yes.  Not orthogonal usually means you haven't taken up any Dec Backlash before Calibrating. Pulse the mount north until you see the guidestar move, THEN Cal.

Sounds like you're using ASIAir, which has discarded some of the important PHD2 features.

Michael

[alacant]

1 hour ago, michael8554 said:

you're using ASIAir,

Really? The OP says he's using EKOS.

1 hour ago, michael8554 said:

Pulse the mount north

Again? This is done in software before calibration.

Confused!

Edited April 26, 2021 by alacant

[michael8554]

5 hours ago, alacant said:

Really? The OP says he's using EKOS.

So he does. Nowhere in the description of the problem, only in the title.   My bad.

5 hours ago, alacant said:

Again? This is done in software before calibration.

Confused!

Is that in Ekos ? Doesn't seem to be doing the job then.

Michael

[alacant]

5 minutes ago, michael8554 said:

Doesn't seem to be doing the job

Mmm. I wonder.

Maybe the OP will post the log.

[teoria_del_big_bang]

Can you give us some more info on your setup ?

Sounds to me you are using PHD2 selected in EKOS is that right, or is it the EKOS internal guider ?

Can you post a guide log of a good night where the RMS is 0.5 to 0.7 RMS and a night it goes wild and maybe some screen shots of the guide graph.

Steve