Went out last night to the Melbourne fringe and tested this Sigma 30mm f 1.4 lens. It's not the Art series lens so the quality isn't as good and at f 1.4, it's virtually useless for astrophotography. I stopped down to f 4 to help eliminate the coma, still no good, f 5.6 still had coma, f 8 and there was signs of improvement. I left it there and shot 16 x 2 min subs @ 1600iso with the modded Canon 550d mounted on a Nano Tracker. I think f 11 would have eliminated the coma but stretching the exposure to 4 mins on the Nano Tracker to compensate, was out of the question. Consequently, the test established that I won't be using this lens for astrophotography.
