Uneven black border around image after stacking

[Andyy]

Uneven black border around image after stacking. A thin black border due to dithering is ok,  but is this normal?

It happens last night when doing automatic meridian flip in NINA. I've stacked subs before and after meridian flip and only show a small thin border caused by dithering. Only when I stack all subs toghether I get this result.

Edited February 3, 2022 by Andyy

[scotty38]

Looks like the framing is rotated slightly after the flip, did you plate solve etc afterwards? No idea if this is the reason just wondering....

[Andyy]

8 minutes ago, scotty38 said:

Looks like the framing is rotated slightly after the flip, did you plate solve etc afterwards? No idea if this is the reason just wondering....

Yes, exactly but I did not touch camera (or mount). NINA did the automatic flip. I did not plate solve after flip

[scotty38]

Is there any chance the camera has moved of its own accord?

[ONIKKINEN]

Some rotation after a meridian flip should be expected. If your polar alignment is less than perfect = which it almost always is, your DEC and RA are not perfectly 90 degrees from each other (also the case), your camera is not perfectly level etc you will have this kind of rotation.

This looks pretty mild to me actually.

[Andyy]

18 minutes ago, scotty38 said:

Is there any chance the camera has moved of its own accord?

There is no way this can happen. It's screw connection and it is very tight. I've checked

[Andyy]

18 minutes ago, ONIKKINEN said:

Some rotation after a meridian flip should be expected. If your polar alignment is less than perfect = which it almost always is, your DEC and RA are not perfectly 90 degrees from each other (also the case), your camera is not perfectly level etc you will have this kind of rotation.

This looks pretty mild to me actually.

Good to know. Almost never do meridian flip

[teoria_del_big_bang]

If not plate solving after the flip I am amazed it is not more severe.

I take it you do not have a rotator and so the images were upside down after the flip ?

If so them just as @ONIKKINEN says there will be some error after the flip.

Steve

[Elp]

Looks pretty mild, if you're imaging over time this will happen as the stacking process is trying to align all frames so some will be at extremes.

[Andyy]

15 minutes ago, teoria_del_big_bang said:

If not plate solving after the flip I am amazed it is not more severe.

I take it you do not have a rotator and so the images were upside down after the flip ?

If so them just as @ONIKKINEN says there will be some error after the flip.

Steve

I'm pretty sure NINA plate solves after meridian flip. I thought maybe it was an operator error but seems like a common issue:

[scotty38]

16 minutes ago, Andyy said:

I'm pretty sure NINA plate solves after meridian flip. I thought maybe it was an operator error but seems like a common issue:

It is an option that needs to be set on - "Recenter after Flip" in Options/Imaging

[Andyy]

15 minutes ago, scotty38 said:

It is an option that needs to be set on - "Recenter after Flip" in Options/Imaging

Thanks! The setting is "ON"

But what happens then if I've used frame wizard and framed slightly off target center

[teoria_del_big_bang]

1 minute ago, Andyy said:

Thanks! The setting is "ON"

But what happens then if I've used frame wizard and framed slightly off target center

It should re-centre to same position as before the flip, only just started using NINA but most software tries to platesolve to same coordinates as the images before the flip.

Steve

[Andyy]

3 minutes ago, teoria_del_big_bang said:

It should re-centre to same position as before the flip, only just started using NINA but most software tries to platesolve to same coordinates as the images before the flip.

Steve

Perfect!

[teoria_del_big_bang]

It must have worked otherwise I think the frames after the flip would be much further out that the slight rotation error you get there, a small crop is normal on all stacks to get rid of the uneven border, so I don't think there is anything wrong whatsoever there. 🙂 

Steve

[carastro]

Looks like a slight amount of Cone error after a Meridian flip, I get that too.

Carole 

[adyj1]

2 hours ago, Andyy said:

Thanks! The setting is "ON"

But what happens then if I've used frame wizard and framed slightly off target center

Just for completeness, the explanation of this is that the framing wizard sent the co-ordinates of *your adjustment* as the target of your sequence, not the original co-ordinates. When the meridian flip occurs NINA only knows to re-centre on the the co-ordinates of the framing you chose, not the original framing. 

Which is exactly what you want 🙂