[Ads (Ads)]

Hi all,

Finally got some sky time for my scope - running a GSO RC-6", on a iOptron CEM26 mount, Canon 650D.

No adjustment to collimation since 2nd-hand purchase, have installed a focus/collimation plate since, also unadjusted.

Had a pretty nice run, but after stacking, I'm seeing some smearing in the 'bottom, bottom-left' stars in these images.
I was concerned it may be flexture from the backfocus etc, but different sky locations seem consistent.

De-focused stars show pretty good collimation just from a quick glance - my guess is the focuser/extension tubes being a bit off-axis.

What do we reckon?
Could well be that the camera/sensor isn't sitting in-plane.
I thought it may be that the extension tubes are angled off enough to be off the edge of the image-circle.

Bit frustrating in using a DSLR, ~8sec readoff time - maybe can run some 30sec exp's in a star-dense region to do checks between adjustments, hopefully can catch the clear sky tonight (not been good skies in Sydney lately!)

Single frames show vignetting in corners, my guess is just in having a 1.25" nosepiece on the T-ring - considering a 2" nosepiece as the focuser only has a single thumbscrew on the 2-1.25" adapter - two thumbscrews on the 2", so would get a more affirmative fixture in that case.

I've lost the links I had to some of the software that would analyse the flatness etc - if there's some suggestions?

Overall, just wanted to see what people's thoughts might be regarding the smeared stars, and the likely cause/adjustments needed.

Thanks all!

Clear skies!