Re: ATM Big Bad Cheap Lenses?

["Frank Ward" <thewards@mindspring.com>]

but in the meantime, any lines on larger
> but comparitively low quality bi convex lenses would be great.

E-Bay is filled with them. They are called projection lenses.

Frank Ward
Atlanta, GA

----- Original Message -----
From: "Robin Coope" <rcoope@physics.ubc.ca>
To: <atm@shore.net>
Sent: Friday, February 01, 2002 6:08 PM
Subject: RE: ATM Big Bad Cheap Lenses?


>
>
> Thanks for all the ideas.   We actually started with a relay lens system
> made from fresnel lenses spaced at 2f, but if if you use any more than
four
> fresnel lenses you start to get unacceptable degredations in quality. I
said
> that quality wasn't much of an issue, but I was thinking in terms of
normal
> optical standards, where you want to resolve the doubles in epsilon Lyrae
or
> whatever.
>
> I am in fact using an infinite conjugate relay lens system now, which is
> essentially two telescopes facing each other.  I should revisit that and
try
> making a small-lens finite conjugate relay system in between the Fresnel
> lenses.  If I could use 3" lenses it would be easy to find ones of the
right
> focal length that aren't outrageously expensive.  I think though, that the
> larger the lenses I can get, the better the viewing angles, which while
not
> critical, would be nice.  I will experiment this weekend using some 1"
> lenses I have in my optics cabinet, but in the meantime, any lines on
larger
> but comparitively low quality bi convex lenses would be great.
>
> I shall let you know.
>
> Thanks,
>
> Robin Coope
> UBC Physics and Astronomy
> Genome Technology Lab
>
>