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Copy Scope Eyepiece Recommendations?

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Posted by Ted Bruce on October 16, 2003 16:46:28 UTC

I just joined the forum, I'm a newbie when it comes to optics. I have a copyscope I made using the design and lens from the supplier in the Astronomy magazine 1986 issue. I'm upgrading this scope for my grandson, and I have some questions:

1) I have a .965 focuser pulled from a cheap 60mm dept. store scope. I want to use this with a 1.25 eyepiece adapter. The focuser has a circular baffle with a 1/2 inch hole. Should I remove this, or put in a different size?

2) On another forum from a couple of years ago, a contributer said that the lowest useable power is 4 x the objective diameter, and 6 to 8 x is better. The copier lens I have is an f4, 280mm focal length, with a lens diameter of about 3.2 inches (81mm) for the front and back lenses. There *appears* to be an slight internal baffle in the lens; I have no way of measuring it.

Using the TEC calculator, I get 31 power, exit pupil 2.6mm for a 9mm eyepiece; and 23 power, 3.5mm for a 12 power eyepiece. Are these exit pupil diameters acceptable? The powers are well within the ranges specified in the other forum posting.

3) Would the calculations be the same for either .965 or 1.25 inch eyepieces?

4) I'm also planning a second copyscope using an identical copier lens, with a 1.25 inch focuser that I bought from a surplus outlet. Will the same calculated values hold true?

5) I have 26 and 15mm Meade Superplossls that I got with my LX100 8" about 12 years ago, and a Celestron 32mm Plossl that I just bought on eBay. Apparently, the 15mm will be the only useable one for my new copyscope, correct?

Does anyone have any recommendations, or validation of my computations?

Thanks in advance,

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