Collimation advice please

[rubecula]

I'm getting oddly shaped stars when imaging 600 sec exposures with the 8" EdgeHD scope and think it might be due to poor collimation. I did try collimating with Polaris but as I have had 2 discs removed from my neck I find it very difficult to look through the scope when it's near the zenith.  So, I bought a Hubble Artificial Star and checked the scope this morning. On the outside of focus I only managed to get a single dark outer ring but things looked symetrical.  On the inside of focus I was unable to get any clear rings as things were very fuzzy.  I was testing with the focal reducer in place but without the diagonal (as I always do when imaging) and a 13mm Baader Hyperion lens with both fine tuning rings which makes it equivalent to an 8.1mm lens.  I think that gives me a magnification of x172.

Is that enough for a collimation test?

Does the difference either side of focus indicate a collimation issue?

 

[PeterCPC]

If you cannot look through the scope at Polaris, why not use your Canon and BYE?

Peter

[rubecula]

I didn't realise it was possible to use BYE and a camera too check collimation.  I've used Frame & Focus to get focused for imaging but not for collimation.  Is it easy?

[PeterCPC]

Just use Live View and take it in and out of focus as you would visually. Pretend that you are using a Batinov Mask to get focus - it's the same principle.

Peter

[rubecula]

Thanks Peter