Summary

Useful for RC collimation, or any telescope, but RC's benefit from the field for stars. Place a good distance from the scope (distance depends on focal length). The ball bearings are 15mm diameter and I've coated it in felt for increased contrast. Included is an acra swiss plate which can be glued to the back for tripod holding. (Was a bit of an after thought).

On a bright day the suns reflection off the bearing made a good point source of light. Alternative shine a bright artificial light at the starfield and you'll get the same effect. Angles aren't super important.