I am slowly restoring a Cave 12.5" F/6 and plan to change a few things. The scope will be original as much as possible though the focuser will be replaced with a Moonlite. My intentions are to set the scope up for binoviewing and a low profile focuser will be part of the plan. At present the scope has a 2.6" secondary and I am inclined to replace that with a 2.14" to get a smaller CO. Will this work with a binoviewer or do I need to stay with the 2.6" for a fully illuminated field?
Diagonal size question
Started by lthaxton, 08/24/2008 02:33PM
Posted 08/24/2008 02:33PM
Opening Post
Posted 08/24/2008 03:01PM
#1
What is the tube diameter?
A Moonlight focuser has 1.6" height. Assuming the tube diameter is 14.5", and you want 0.25" spare in-focus, a 2.14" secondary will give you a 0.7" fully illuminated field, and 1.45" 75% illuinated field, which should be plenty. You could even drop down to 1.83" if you wanted to make it a planetary scope (100% zone would still be 0.3", plenty for planets, but you might see vignetting in wide field eyepieces - the 75% zone would only be 1.1").
Jarad
A Moonlight focuser has 1.6" height. Assuming the tube diameter is 14.5", and you want 0.25" spare in-focus, a 2.14" secondary will give you a 0.7" fully illuminated field, and 1.45" 75% illuinated field, which should be plenty. You could even drop down to 1.83" if you wanted to make it a planetary scope (100% zone would still be 0.3", plenty for planets, but you might see vignetting in wide field eyepieces - the 75% zone would only be 1.1").
Jarad
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