Farpoint 1.25 Inch Cheshire Collimator is a simple tool that helps align the optical axes of the mirrors of a Newtonian Reflector, a process called collimation. This precision-machined, blue anodized alignment tool for 1.25" apertures is practically indestructible and requires no batteries.
A Cheshire eyepiece or Cheshire collimator consists of a peephole that is inserted into the telescope focuser in place of the eyepiece. Ambient light falls on the brightly painted oblique back of the peephole. Images of this bright surface are reflected by the mirrors of a Newtonian Reflector and can thus be seen by a person peering through the hole. A Cheshire eyepiece contains no lenses or other polished optical surfaces.