ASI2600MC Pro and Elongated Stars

viksmi

I recently bought a ASI2600MC pro and had couple of sessions with it no problems. But this weekend I was trying to get started with another one but encountered a problem. I started seeing elongated stars. I have read numerous discussion regarding this and I can come up with couple of reasons this could happen:

issue with back focus
camera tilt

I kind of want to rule out back focus as it's well established for my setup its 55mm. I have this optic train:

ED102CF->HoTech 2" Field Flatterner->Spacer Ring(21mm)->Spacer Ring(16.5mm)->ASI2600MC PRO

So my setup has 21 +16.5+17.5 = 55mm

and this setup has been working for me, at least two weeks since I bought the new camera.

The second issue that I suspect could be camera axis tilt as my HoTech gets inserted into adapter ring I feel that might not be aligned properly as it has 3 knurled screws that needs to be adjusted. Or It could also be the Camera itself, I am not sure.

My question is - how do I find out the cause for the elongated stars? I tried to adjust the adapter ring but its not changing anything.

I would appreciate if somebody could point me to right direction to fix this issue.

Thanks
Vikram

Kevin_A

viksmi if it is just in all four corners it is backfocus spacing, in 1 or 2 corners is tilt and all over it is guiding issues.

viksmi

Thanks for pointing out that. My case its elongated all across but question is why is it happening for 10s exposure? I do that all the time and I don't see this kind of stretch on the stars?

Adding the snapshot of the image in case you want to take a look.

for some reason I cannot upload the image. But it's stretched all across and in the same orientation.

viksmi

Just FYI, I noticed the elongated stars not while I was doing my imaging but while I was doing initial setup and right away stated troubleshooting. Normally I take 5 or 10s exposure to check the stars for focussing purposes and that's where I got stuck. If this is a sign of guiding or maybe mount not being level or something willl spend more time on that and check this evening. I was worried that there might be some issues with the camera axis !

Thanks

viksmi

Kevin,

Thank you so much for giving me the hint. I was going to troubleshoot all over the place thinking it could be Camera axis issue. You put me in the right direction. Turns out it could have been either the mount level or the telescope balance that might have been off the other day resulting in elongated stars. I took time today to make sure I got the covered and the result it wonderful. I was able to get my regular imaging going....appreciate it !

Kevin_A

viksmi you are welcome… glad I could help steer you towards the correct avenue to look at! Cheers!