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vingetting with focal reducer?

Started by y, 03/04/2005 05:50PM
Posted 03/04/2005 05:50PM Opening Post

will a meade 24.5 mm SWA (67 degree apparent FOV) have a problem with vingetting if i use a .7x focal reducer in my 8" f10 SCT?

using nexstar 8 gps, denk II power X switch with star sweeper


Posted 03/04/2005 09:48PM | Edited 03/04/2005 09:49PM #1
Bill, if you're talking about a reducer and a binoviewer, it shouldn't. My binoviewer works just fine in my SCT with 24mm wide angle ep's and .6(?) reducer. No vignetting that I can see. What didn't work was trying it with my .63 SCT reducer. Wouldn't come close to focus. If you're viewing mono it should work great.

Mark Rice
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Posted 03/05/2005 02:14AM | Edited 03/05/2005 04:36AM #2

I agree with Mark. If the eyepieces you are using are not vignetting then they will not vignette with a focal reducer designed to work with your equipment. The biggest problem I have seen so far when using focal reducers with binoviewers is reaching focus. As a general rule of thumb, The closer you can get the focal reducer to the nose of the binoviewer the better chance you will have of reaching focus. The further the focal reducer is from the binoviewer the greater the focal reducer effect will be.

Using too powerful a focal reducer could cause the field of view to shrink and appear as vignetting.

Don Durbin