Hi Pat - Your photo at f/2 looks pretty similar to what I get with that lens. Yes there is coma in the corners, and it shows up as radial streaks through the stars. After seeing how bad it was at f/1.4, I was actually quite pleased with the performance at f/2. I have another chance at northern aurora photography in a few weeks, and if I get bright lights then I will try shooting at f/2.8 and even f/4 to see the difference. But the coma at f/2 doesn't bother me at all... it's a negligible tradeoff for the ability to shoot at a faster shutter speed.
For reference, here is the Perseid meteor shot that I posted a while ago, taken at f/1.4. This shot is uncropped, so you can see the extent of the coma in the corners. Since then I shoot at f/2.
Last edited by Jonathan Huyer; 10-09-2013 at 05:30 PM.
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