The 25mm/2 is an excellent lens, well corrected for both lateral and longitudinal chromatic aberrations, and quite flare resistant. I love mine for urban night photography, but for wide-field astrophotography it\'s not as good. Coma deformations of stars are bad in the corners at f/2 and f/2.8, so you have to stop down to f/4 for round stars, but that will necessitate very high ISOs, stacking, or a tracker mount. There is also a fair amount of forward field curvature, but this isn\'t bad, and for landscape work with close foregrounds, it actually helps sharpen the foreground.
The 25mm/2 is an excellent lens, well corrected for both lateral and longitudinal chromatic aberrations, and quite flare resistant. I love mine for urban night photography, but for wide-field astrophotography it\'s not as good. Coma deformations of stars are bad in the corners at f/2 and f/2.8, so you have to stop down to f/4 for round stars, but that will necessitate very high ISOs, stacking, or a tracker mount. There is also a fair amount of forward field curvature, but this isn\'t bad, and for landscape work with close foregrounds, it actually helps sharpen the foreground.
