3 replies to this topic

[homerdt]

Ok, I'm totally at a loss, last night I went out and got a crapload of frames with my new lens. Rokinon 14mm f2.8mated to my ZWOASI071MC Cooled, as I was going through my frame and focus routine I noticed that when I got good focus on the screen the focus ring showed that it wasn't on infinity. But I had good focus on the screen. Today I started processing and after stacking it showed on DSS a good image but when I opened it in photoshop This is what I got. I'm totally at a loss, TOTALLY.... Anybody?[attachment=1560963:Screenshot (1).jpg][attachment=1560965:milk.jpg][attachment=1560967:baffled.jpg]

[bobzeq25]

Can't see the files.

[homerdt]

Can't see the files.

Forget it, I think I figured it out. Can't figure out how to delete this post.

[RandomJoe]

Do the stars radiate out in all directions from the center?  I had similar trouble using a Rokinon 16mm lens with my 1600mm, and after much searching of forums I believe it's down to the spacing.  The fast lenses are VERY sensitive, even a half-millimeter shim can make a big difference.  I never did get mine looking right, but I did find some other threads here with what seemed to be relevant info, including this one:

https://www.cloudyni...00mm/?p=9992621

 

Which includes two images showing what the stars do if your backfocus is too short or too long.  That thread is referring to a refractor with field flattener, but I believe it would also hold true for a camera lens?

 

One of these nights I'll finally give this a try again.  I need some more very thin shims though, I don't think I have what I need to get to the sweet spot.