Advice on ASTAP tilt analysis please

[Stuart1971]

Hello all,

just been rechecking my new set up for tilt, and pretty happy with it now, the images look pretty good, until you pixel peep then I am not sure whether I have the flattener backspacing spot on, so after running one of the raw images through ASTAP I get this, my question as the tilt is minimal, but the sides of the square are slightly pointed inwards, does this indicate flattener distance not correct ?? If so in which direction….??

thanks in advance

 

[ONIKKINEN]

I cant tell from this image what shape the corner stars are, so at least its not obviously wrong.

Instead of backspacing it could also be just the normal loss of sharpness far away from the center of the field of view that happens in almost every imaging corrector. See if you can find a spot diagram for your corrector to confirm that?

[Stuart1971]

I have seen other ASTAP image analysis like these with pretty much perfect squares, so wondered if the figures relate to the tilt and the “shape” of the “square” was curvature due to incorrect backspacing…🤔🤔