Bower 800mm f/8 Manual Focus Telephoto Lens for Pentax Screw Mount (M42)

The Bower 800mm f/8 Manual Focus Lens is a catadioptric mirror T-mount lens, precision manufactured in South Korea.  In this configuration it is delivered with a T-mount for the "M42" screw mount, which is also known as the Pentax screw mount.  There are many different cameras which employ the M42 mount.

The fixed f/8.0 aperture of this lens is not communicated to the Pentax screw mount camera body, and as such you can only use the camera in the "M" manual exposure mode or the "A" aperture-priority mode (if your camera is so equipped).

This lens, at 4.4 x 5.2" and just over 2 pounds, has a broad diameter and stocky build.  It is a bit easier to handle than a normal 800mm refractor lens, but it is still a super-telephoto in any case (you should use a tripod/monopod in any case for best results).  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).