I want to use my binoviewer with a Celestron scope. How much back focus does it need?

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	I want to use my binoviewer with a Celestron scope. How much back focus does it need?

Answer Binoviewers have a string of prisms inside that bend entering light through a path of several inches as the light is split and then brought to a pair of eyepieces. A typical binoviewer for 1-1/4” eyepieces (like the Celestron #93691) uses about 3-1/2” of back focus. Other brands use less and some use more than 4 inches back focus.

This is not a problem for a Schmidt-Cassegrain telescope and its approximately 5 inches of focal accommodation. Many Maks also have large back focus distances.

It is a problem for spotting scopes that take 1-1/4” eyepieces and for Newtonians. They simply don’t have enough back focus to use a binoviewer. You won’t be able to focus on infinity using a binoviewer with these scopes.

Article Details

Article ID:

2478

Created On:

Mar 22 2011 05:44 PM