Re: [APML] Where to get minus violet filter for cameras? (was: Te ch Pan)

[Roland Roberts <roland@astrofoto.org>]

>>>>> "cq" == Quintero, Chuck -Gil <Chuck.Quintero@itt.com> writes:

    cq> I bought a 52->48mm adapter from the camera shop for $5, and
    cq> it works fine.  There's no vignetting for a 200mm lens.

Actually, I have done that as a quick hack to use an LPR filter on
some of my lenses.  That's enabled me to get some test shots even from
here in New York City.  And while I'm not using the nice
color-balanced Hutech LPR (I bought the Orion one for $80), it works
for my purposes.

However, a 200mm at f/4 has a 50mm clear
aperture.  With the filter sitting out in front of the lens, there is
a little vignetting in the corners.  A 135mm at f/4 (about as fast as
I can use on my 135mm lenses without unacceptable aberrations off
axis) has no noticeable vignetting.

So using the 48mm has occurred to me, but I'd rather have a larger one
and use step-down rings to fit on smaller lenses.  That way the filter
will never be the limiting factor (I have enough limiting factors
already!).

roland
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