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vingetting with focal reducer?

Started by y, 03/04/2005 09:50AM
Posted 03/04/2005 09:50AM Opening Post
hiya

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

thanks

bill
Posted 03/04/2005 01:48PM | Edited 03/04/2005 01:49PM #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
Keep it dark, or at least keep it quiet. wink
Ultima 2000... and other things
Posted 03/04/2005 06:14PM | Edited 03/04/2005 08:36PM #2
Bill,

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