I recently purchased a used Sigma 60mm f/2.8 lens for astrophotography and I could not be happier with this purchase. This shot is composed of 44 light frames of 3 minutes at f/2.8 and ISO 800 along with darks and bias frames. I also used an Orion Skyglow light pollution filter and it was guided with an Ioptron Skytracker. This lens is pretty amazing...no coma at all wide open. There is just a touch of CA and a bit of vignetting which can be corrected with flat frames although I just cropped it out. For $150 (used), this lens is way worth it. Cheers!