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projection TV lenses
The other day at a garage sale a projection TV was for sale. Looking at the
projector lenses I wondered if they could be used to make a refractor. The TV was faulty and probably can't be fixed for a resonable price. They appeared to be about 90 or 100mm diameter. Considering that the projection reflects off a mirror and onto the screen, the FL would have to be maybe 400mm or so. Any ideas on this? |
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projection TV lenses
On Sun, 16 May 2004 22:17:07 GMT, "Thomas" wrote:
The other day at a garage sale a projection TV was for sale. Looking at the projector lenses I wondered if they could be used to make a refractor. The TV was faulty and probably can't be fixed for a resonable price. They appeared to be about 90 or 100mm diameter. Considering that the projection reflects off a mirror and onto the screen, the FL would have to be maybe 400mm or so. Any ideas on this? My guess would be that their correction for chromatic aberration is somewhere between poor and non-existent. Since in the TV each is only focusing a relatively narrow part of the spectrum, such correction is not necessary. They will also be designed to produce a large, flat field (in projection) which will probably translate to some unusual distortion when used in telescopes. _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
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projection TV lenses
" My guess would be that their correction for chromatic aberration is somewhere between poor and non-existent. Since in the TV each is only focusing a relatively narrow part of the spectrum, such correction is not necessary. They will also be designed to produce a large, flat field (in projection) which will probably translate to some unusual distortion when used in telescopes. _________________________________________________ Ok. Sounds good |
#4
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projection TV lenses
"Thomas" wrote in message news:GwTpc.7566$9P6.98@clgrps12...
" My guess would be that their correction for chromatic aberration is somewhere between poor and non-existent. Since in the TV each is only focusing a relatively narrow part of the spectrum, such correction is not necessary. They will also be designed to produce a large, flat field (in projection) which will probably translate to some unusual distortion when used in telescopes. _________________________________________________ Ok. Sounds good I emailed with someone who tried it, and Chris hit it on the head --- a waste of time making it into a scope. Clear Skies Chuck Taylor Do you observe the moon? Try http://groups.yahoo.com/group/lunar-observing/ And the Lunar Picture of the Day http://www.lpod.org/ ************************************ |
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projection TV lenses
"Thomas" wrote in message news:DLRpc.16863$0e6.2779@clgrps13...
The other day at a garage sale a projection TV was for sale. Looking at the projector lenses I wondered if they could be used to make a refractor. The TV was faulty and probably can't be fixed for a resonable price. They appeared to be about 90 or 100mm diameter. Considering that the projection reflects off a mirror and onto the screen, the FL would have to be maybe 400mm or so. Any ideas on this? Projection TV lenses tend to have a relative aperture of about f/1, and have many waves of residual aberration. Some of the newer ones for HDTV are quite good, and some are now fully color corrected, but may not be available in garage sales for some time! Brian www.caldwellphotographic.com |
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projection TV lenses
You've got your choice of three, the red, green or blue.
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