Object not centered after meridian flip - Forums

Topic starter

Jul 22, 2023

Hi all. I have a question regarding meridian flips and plate solving.
I have an EdgeHD11 on an AP1100 mount. I use NINA and ASTAP in my suite of software tools.
Last night I started my sequence run of 18x600s Ha followed by 18x600s of Oiii on M27. I had centered M27 prior to the run. After the meridian flip M27 was offset from center by about 56" (nearly 1 arc min). Since the coordinates were preset at the beginning of the sequence, I'm not sure why ASTAP/mount couldn't center the object after the flip.
Any ideas?

Well Written Engaging

Björn Arnold

Jul 22, 2023 · Edited: Jul 22, 2023

In NINA, there's a setting called "recenter after flip" which you might need to turn on. You'll find it in Options -> Imaging under "Meridian flip settings".

If you work with the advanced sequencer, I recommend also to include the "recenter" trigger which monitors over the course of imaging if the image center has shifted beyond a certain limit and triggers a recenter.

Björn

Well Written Helpful Concise

Brian Puhl

IOTD Staff

Jul 22, 2023

Like Bjorn said, recenter after flip, and then in your triggers make sure you have 'recenter after drift'. Even if it fails on flip, it will find itself again after X exposures.

I would also add you SHOULD put refocus after flip in your meridian flip settings as well. If there's any slop in your imaging train, it could get thrown out of focus after flip, possibly causing a plate solve failure

Helpful

Guiem Kimi

Jul 22, 2023 · Edited: Jul 22, 2023

Just to add some info here, logs in NINA give lots of info about what is happening during the session. You can find a button which open it's folder in Options > General > Logging

For example, I had a failed flip in one of the last sessions and thanks to the logs I realised it was because of an EQAscom AR limit misconfiguration.

Clear skies,
Guiem.

Helpful

Scott Lockwood

Jul 22, 2023

I'm not familiar with NINA but I do have a AP1200 mount. The AP should nail it. My though is- did you finetune the location of M27 after you slewed to it? If so, did you re-sink on the object as if not, the flip would go to the first location.

Oskari Nikkinen

Jul 22, 2023

I also use NINA and find that sometimes it is not within tolerance even with the relevant settings ticked (the recenters and such already mentioned). I suspect that for some reason NINA defaults to the default platesolving tolerance (which i believe is 1 or 2 arcmin) after an automatic re-center post meridian flip, whereas you could have set your tolerance to a lower value.

Anyway i have not bothered to look into it closer and just re-center again after a meridian flip and get the correct framing. I am sure there is some more elegant automatic way of doing it, but what works is good enough for me.

Helpful

Michael J. Mangieri

Topic starter

Jul 23, 2023 · Edited: Jul 23, 2023

Thank you all for your input. I think I did finetune the location (as Scott mentioned could be part of the problem). I already have the recenter after flip but will add the refocus after flip command in my sequence for tonight and see what happens. In this hobby there is always something new that you didn't know about. What makes this hobby fun, I guess

Scott Badger

Jul 23, 2023 · Edited: Jul 23, 2023

If you have re-center after the flip enabled, but don't have the coordinates of your target in the sequence, then NINA will platesolve to the coordinates that the mount thinks it's pointing at, not necessarily the target. I'm not sure why there's a difference, whether it's due to the pointing adjustment after the initial platesolve (before the meridian flip), or the drift while not guiding when NINA pauses the sequence before the flip. Not sure how that would work, but the problem seemed worse when I was imaging in Ha where the longer exposures tend to result in longer pause times. Anyhow, Cuiv mentions it in one of his videos, https://www.youtube.com/watch?v=lAMyEpBcLV4 (at about 15:40). Whatever the cause, adding my target coordinates to the sequence made the problem go away for me.

Cheers,
Scott

Helpful Insightful Respectful

Michael J. Mangieri

Topic starter

Jul 24, 2023

Looks like I may have adjusted the position prior to running the sequence and so when the flip was completed NINA used the incorrect coordinates to center on. Tried again by using the framing assistant to get the actual location, saved that as a target and ran the sequence. All is well now. Thanks everyone.

Helpful Concise