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TV projection lens = telescope??

Started by danielfreas, 04/05/2002 05:13PM
Posted 04/05/2002 05:13PM Opening Post
I've got this 4.5" TV projection lens that I bet would make a great telescope. Has anyone done this before? I'd appreciate some advice, and if there are any websites out there with plans for this I'd appreciate a link.

Posted 04/05/2002 05:32PM #1
Someone is selling them on Ebay and claims good results. Somebody that knows optics can probably give a long list of why its not so great. But hey, if its jsut for giggles and you know its not going to equal a $4000.00 scope then what are you out?
Posted 04/05/2002 05:43PM #2
Well from what I can figure so far the focal length on this lense is incredibly short, probably not even as long as the lense is wide so planetary viewing is right out. Maybe a good kick around scope for the moon would be possible though. I'm thinking about taking it apart and using the lenses separately instead of as an assembly.
Posted 04/05/2002 09:29PM #3
I finally managed to disassemble this thing (riping off half a fingernail in the process) and found a whole bunch of lenses inside. One of the lenses seems to be a 90mm f/2.5 that would probably work in a copyscope type design.

Another one of the lenses is very odd and I'm hoping someone here on the forum can tell me what it is and what I can do with it. It's obviously two lenses that have been cemented together, one of the lenses is *extremely* concave to the point of resembling a soup bowl. Then the other lens fits against this one but has a flat side facing out. So as a whole one side of the pair is very concave and the other side is completely flat. Besides a paperweight what's this good for??