[davidmanze]

, 

Ok, just a couple of days ago we were discussing about UWA and coma. I said that the Samyang 12mm Æ’/2 has excellent reviews in this respect, I own it but I hadn't find the time to test it yet.

 

So, yesterday I thought it was high time for that. No, I wasn't able to shoot at the Perseids: I actually prepared everything in the garden, but then I waited for the moon to set and... in the meantime I fell asleep.   I'm really not an astrophotography man, apart from some rare exceptions. 

 

In any case, during the preparation I did shoot a couple of tests... and I was surprised. The crops below are at mid height, from the extreme left and right borders. At the left border there's no sign of coma. At the right one, it's quite evident. It starts to be visible at the rightmost 1/4 of the image, and annoying at 1/10. No big deal: knowing it, it's just a matter of properly composing so that I later crop a bit.

 

But now I'm curious: is this a sign of decentering?

 

PS Full aperture, of course, and - for what matters - 30sec, ISO 200, Sony a6000.

The crop of the yacht marina shows softness at the right edge which "if" it is not there on the left side shows de-centerering. The two star shots the left shot  shows coma, the right looks like star trail! 

 If the lens "is" de-centered return it for another. Futher checks on distant views of tree/foliage the toughest test!