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Post by Aaron on Sept 23, 2004 10:43:27 GMT
Can anyone give me some advice. For part of a course i have to make a home made telescope, so im going to attempt to construct a refractor. Does anyone know how thick the primary lens should be? Can you get different thicknesses?
Aaron
;D
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Post by paulevans on Sept 27, 2004 7:23:23 GMT
Yes there are different thicknesses but that is not the dimension that is important. What matters is the focal length of the lens and this is a factor of the thickness of the lens and the refractive index of the glass. The eyepiece consists, in the very simplest design, of a second lens placed close to the primary focus of the objective lens so the length of the tube will need to be roughly the same as the focal length of the objective lens.
Hope that helps.
P.
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Post by markdj on Sept 27, 2004 15:29:30 GMT
I concur with Paul. If you really want to do this and spend a bit of money, have a look at apochromatic doublet or triplet. The Orion ED APO series uses the Chinese FPL-53 which is a synthetic flourite and is the same glass that Astrophysics use as there ED element.
An f/6 or similar quite fast focal ratio would be what to look for.
Not sure if you are making a focuser from scratch but the Williams Optics focuser is recommended. Go for a Crayford focuser which will give zero backlash. Make sure you have a way of getting very fine control for movement of the focuser so you can collimate the two. A chesshire eyepiece is good for this too.
Good luck
M
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Post by Aaron on Sept 28, 2004 9:59:12 GMT
Hey everyone Sorry i didnt get back to you Mark re: the email you sent. I've been thinking about the telescope construction for the past couple of days and whether to go for proper materials or a simple design. I think for the time being I will construct following Paddy Moore's simple design in the text book. (cheaper by far as I dont really have a budget especially for an apo lens)
I got a reply on the cloudynights site and was directed to this site. (http://www.apogeeinc.com/scopeoptics.html) There is a mountain of optics and accessories for the keen builder. They are quite reasonably priced as well - 90mm lens with a 1000mm FL for $85, what do yous think?
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Post by markdj on Sept 28, 2004 10:18:33 GMT
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