Distortions... focus? optics?

[chd]

I seem to be fairly consistently getting stars that look like the attached example - note especially the Don King hairdo blur on the top side.

Is this a focus issue? Collimation issue? Tracking issue?

Also, I find that bright stars don't just get big, they get like huge dinner plates - is this normal bleed from oversaturated pixels to their neighbors, or does this image suggest an addition allue contributing?

Thanks!

[jambouk]

How is the image acquired exactly and using what kit? Knowing this will help work out the problem and potential solutions.

I suspect there may be more than one issue; focus i would guess is the main player.

James

[ronin]

If the equipmwent is as stated in the signature:

Celestron CPC 8" SCT with altazimuth mount, HyperStar + Atik 428ex

Then I would guess a combination of items.

Long focal length of the CPC means tracking has to be accurate, very accutrate.

The mount will track wrong so giving some distortion - Alt/Az mount show field rotation over time.

Can you check collimation, more to know the status of it.