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Old May 21, 2012, 7:14 PM   #1
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Default question about lenses

I have a GE X500 (16 mp and 15 times optical zoom) which is hard to find info for as far as digiscoping is concerned. I guess this model has not been around for long. I've been doing further research and it seems that long zooms like this cameras' 15 times optical zoom are not as good as 3 to 4 times zoom. From what I understand that's because the eye of the zoom lens on the long zoom camera is bigger than the eyepiece of the scope. My question is about my camera -the glass covering on the lens front is 40 mm but the the lens underneath is about 14mm. I assume they are talking about the 14 mm lens? If so, should it be good for digiscoping if the eyepiece of the scope is larger than 14 mm and is that easy to find or am I misunderstanding something here?
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Old May 21, 2012, 7:49 PM   #2
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The eyepiece of a telescope is (more or less) a projecting lens, and works like the overhead projectors that are (used to be?) used in school, in that the farther away they are, the larger the image is. They are made to give an image roughly the same as your eye's pupil opening when looking directly into the eyepiece. (about 5mm max) The farther away, the larger the image, so you should be able to get any size you want (within reason), by moving your camera closer or farther away. This needs something like a sliding tube arrangement. Matching the image circle to your camera lens will give you the most light transmission. You can find the distance you need by using translucent plastic sheet or onionskin type paper, and making a circle of the size you want, then measuring the distance from the eyepiece when they match. (you need a pretty bright sky or something that fills the view - not the sun or a point source of light)
Hope this was of some help.

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