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Old Mar 2, 2004, 9:51 PM   #11
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500mm/8=62.5
The objective is 62.5mm in diameter.

Of that area the nearly 30mm is obstructed by the secondary mirror. Then it the image has to go through the erecting prism. That furthers reduces the transmitted light. Yep it needs a LOT of light.

I am using a 18mm Scopetronics widea angle eyepiece made especially for digital cameras. 500mm/18mm=about 28X. This one I use with a Nion 995 (4X zoom). I also have a 40mm by Williams optics. 500/40=12.5X. This last one has 43mm lens thread. I use it with a Sony 707 (10X zoom) and an old Casio 8000SX (8X zoom). The problem I have with all the above is focusing . The old Casio is by far the best in this regard (and many others) but it is only 1.3MPixels. Both the Casio and the Sony have to be run out to the MAX zoom to avoid vigeting. The nikon can run the entire zoom range but it is the absolute worst at focusing (manual, automatic, macro or otherwise). If I could fide another Digital camera as good as the Casio with about 2-3 times the pixels I would jump at it. In my opinion both the Nikon and the Sony fall short except for megapixels.

My point about the zoom lens(s) was that in order to use them as a scope you may need to "chop" off the back end. Considering the cost of old SLR screw mount zooms on EBAY this might not be a very espensive experiment ... but it might be a tedious one.

One other point. You can pick up a good 80mm short tube refractor on www.astromart.com classifieds for about around a hundred dollars (sometimes less) ... if you watch.
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Old Mar 3, 2004, 1:33 AM   #12
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Quote:
Originally Posted by LewTwo
500mm/8=62.5
The objective is 62.5mm in diameter.

Of that area the nearly 30mm is obstructed by the secondary mirror. Then it the image has to go through the erecting prism. That furthers reduces the transmitted light. Yep it needs a LOT of light.
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hmmmm....see what you mean. This may be minor. But is it possible to place the erecting part after the viewfinder? You still get the upside-down shot, but you see the right shot.
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I am using a 18mm Scopetronics widea angle eyepiece made especially for digital cameras.
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I'll check that out.
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500mm/18mm=about 28X.
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I guess my only though here is "less power, more light" A longer FL eyepiece would help in bad light situations.
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This one I use with a Nion 995 (4X zoom). I also have a 40mm by Williams optics. 500/40=12.5X. This last one has 43mm lens thread. I use it with a Sony 707 (10X zoom) and an old Casio 8000SX (8X
zoom).
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Ah! There you go! <G>



The problem I have with all the above is focusing . The old Casio is by far the best in this regard (and many others) but it is only 1.3MPixels. Both the Casio and the Sony have to be run out to the MAX zoom to avoid vigeting.
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Yes. This is my problem. the longer the zoom, the worse the vignetting except at max zoom.


My point about the zoom lens(s) was that in order to use them as a scope you may need to "chop" off the back end.
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I have been able to get "mockups" to work by inserting tghe eyepiece into the back of the lens. I was wondering about 2" EPs to avoid vignetting, but of course you could run into trouble there.


Considering the cost of old SLR screw mount zooms on EBAY this might not be a very espensive experiment ... but it might be a tedious one.
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Bah! Aluminium body...bandsaw! What more do you need? <G>


One other point. You can pick up a good 80mm short tube refractor on www.astromart.com classifieds for about around a hundred dollars (sometimes less) ... if you watch.
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Not here, I think (Australia). The post would kill that
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Old Mar 3, 2004, 2:20 AM   #13
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I am using a 18mm Scopetronics widea angle eyepiece made especially for digital cameras.
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Ichecked out the Scopetornics site. All I could find was a much-touted 40mm special wide angle. Any pointers?
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Old Mar 3, 2004, 2:24 AM   #14
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Sorry! Found 'em.
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