The Bower 500mm f 8.0 Manual Focus Lens is a catadioptric mirror T mount lens, precision manufactured in South Korea.When combined with the T mount to fit your camera system, this mirror lens mounts to camera and works on both full frame cameras as well as the APS C style digital SLR cameras. T Mounts are available for all the digital SLR systems, as well as for C mount systems. However, in every case the fixed f 8 aperture is not communicated to the camera body. As such, you can use the lens in M manual exposure mode or A aperture priority mode only.Despite this lens long 500mm focal length, it has a compact 3 x 3.5 size and weighs under 1 pound, making it a bit easier to handle than normal 500mm refractor lenses it should be used with a tripod or monopod in any case . It also has a much different rendering of out of focus areas than a normal lens; highlights will be doughnut shaped rings with more saturation and contrast on the edge of the ring than on the center.This lens is an ideal candidate for astrophotography use when mounted to a Vixen GP2 Photo Guider or other motorized equatorial telescope mount .