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Old Dec 28, 2005, 2:49 AM   #11
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The key issue here is the size of the exit pupil of the telescope/monoscope and the size of the entrance pupil of your camera lens. The former has to be larger than the latter to avoid vignetting and corner light fall-off. Since most monoscopes (or spotting scopes) have small exit pupil, a smaller digicam (e.g., Nikon's 9xx/4500) with focal length approximately 150mm (in 135 equivalent) to avoid vignetting. On the other hand, if your telescope/monoscopecan use 2" eyepiece, you will have a better chance; however, the power of the telescope may be lower.

The F-Adapter and many similar adapters (e.g., the oldest LE-Adapter) share a similar problem. You have to align the eyepiece at the center properly in order to get sharp images. Otherwise, the sharpness of the obtained images may not be even from edge to edge.



Nikon Coolpix 950/990/995/2500/4500/5700, Panasonic FZ-10 and Canon A95 User Guides

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Old Feb 17, 2006, 12:14 AM   #12
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I disagree. Personally I have tried the TC-E3ED on A80. The rear pupil on TC-E3ED only less than 17mm while the A80 has at least 22mm on the front glass. Yet this combo works great at the 3x zoom without any trace of vignetting bringing me photos of excellent sharpness.


E.T wrote:
fotobozo wrote:
Am I doing something wrong or have I wasted my money?
Pretty much both when you bought that.

It could be shortened to this:
Any "extension" with output pupil smaller than size of lens' front element causes vignetting, no matter how much you zoom.
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Old Jul 9, 2006, 1:50 PM   #13
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I have a canon powershot S1 IS and am currently using an orion universal camera adapter for my newtonian telescope. I am considering buying one of these adapters because the universal mount is heavy and hard to align on the eyepiece that I use (25mm plossl). It is possibe to get the camera lens close enough to the eyepiece and zoom in to the max to elminate vignetting. My problem is weight. The scope has to be balanced to track properly and any added weight causes a problem. I do beleive it is possible to use an f-adapter to acheive the desired results.
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