Quote:
Originally Posted by Elio
Thank you David, me too, that's the sharing of night sky's 
I'm sure the problem was focus, I tried to better with processing...and make it worth in the corners
Here the same configuration in focus, take a look
http://www.astrobin.com/95420/G/
Could you say this is a miscollimated optic?  |
Hello Elio, the collimation looks good in your M13 image, but there definitely appears to be a slight collimation problem with the Cygnus Wall image. Look at the corners of the image:
Upper left: stars are elongated radially from the centre of the frame.
Lower left: stars are elongated in a horizontal direction.
Upper right: stars are slightly elongated radially from the centre.
Lower right: stars are quite good.
So, different elongations in the corners is a tell-tale sign of mis-collimation, although if you don't use a field flattener this will also cause similar issues in the corners (though they would look similar in each corner if collimated).