The Celestron Cheshire Collimation Eyepiece helps you spend less time collimating (proper mirror alignment) your Reflector and Schmidt-Cassegrain telescopes, and more time observing with them, which is what everyone wants! Collimating a telescope by eye, without a proper collimating tool, can be frustrating. This instrument is a combination sight tube and Cheshire tool rolled into one devise. The Cheshire tool element has a cut out section with a precise 45° angle reflecting surface. This specialized eyepiece fits into 1.25″ barreled focusers or diagonals.
This collimation eyepiece uses just the sight tube during the daytime or twilight hours, but the Cheshire function means that you can collimate your telescope in complete darkness by shining a red-light flashlight into the 45° angle cut-out of this tool. Never point the cut out section of the collimation tool towards the Sun or you can suffer permanent eye damage when looking through the sight hole. Because it’s a combination tool, some people will forget to otherwise ignore the Cheshire tool cut out section, when making adjustments with the sight tube during the day. The Celestron Cheshire Collimation Eyepiece comes with instructions included on its use.