With this Vixen-compatible prism rail, you can mount not only a camera, but also any small telescope with a photo mount (e.g. 80/400 refractor, 90/1250 Makasutov-Cassegrain) or even a spotting scope on a mount that can receive a Vixen rail.
1/4" threads can be easily mounted on any camera, or using an optional 3/8-1/4" adapter, a photo tripod head. The rail is 120 mm long.