Sigma claims this is the world’s first f/1.4 diagonal fisheye, the unique feature here being its f/1.4 maximum aperture. This alone would make it a very interesting option for astrophotography ...

However, that elite status for super-telephoto lenses has been slowly eroding, and with the 500mm f/5.6 Sport, Sigma may well have shattered the reputation of such lenses as products only ...