what is going on here? Help needed!

[MarkInSpace (Mark)]

I need some help -

The combination of my Sky Rover 115 triplet, sky rover flattener/reducer , a CEM70 and a 2600mm highlights a problem I have - the lower left hand corner of my images always seems to have elongated stars.
I need some help in diagnosing the issue. My guess is this could be one or more of these problems:
-Camera tilt (but why only one corner?)
-Backspace from flattener (again, why only one corner)
-Telescope internal alignment
-Camera not being centered in the telescope (focuser installation issue?)

I've attached a sample image showing the problem as well as a flat (if that helps at all).

I'd appreciate any thoughts...

[MarkInSpace (Mark)]

Any idea why my flat is not horizontally centered? Is that a clue?

[Joshua Bunn (Joshua)]

Hi Mark.



To answer your last question, your flat indicates that your collimation may be slightly off. one possible cause for the elongation.



As you say, it could be a number of things, if it is til, is is in the upper left and lower right also, but just more pronounced in the lower left.


Try rotating the camera if you can and see what happens to the star shapes relative to the chip. If they follow the chip, it could be tilt. If they don't follow the chip, it could be collimation. Try rotating the camera 180 deg and see if the flat frame unevenness swaps to the other side.


regards
Joshua

[MarkInSpace (Mark)]

Thanks for that idea - I will be trying that tonight!

[AdamJL]

Following. My flats are off centre as well. I think it could be collimation

[MarkInSpace (Mark)]

I discovered my rotator tension grub screws was loose, so I was quite excited to see if that helped…
Due to clouds I could not Star test, but the flat was still off-centre.
Also, rotating the camera did not change the off-centredness of the flat. It remained in the same location despite the camera rotating 180 degrees.