Re: [ATM] lensmaker for a very long focus objective

["Bob May" <bobmay@nethere.com>]

The whole telescope would have to be in an upper area of a multistory
building so that the optical path would be above the crowd.  Putting just
the EP down low won't work as the elevation to the Sears Tower can't be that
much (how far away is that building anyway?) although the closer the
building is, the less real focal length should be used as the scope will
quickly find itself in a condition where the focus is way off from the
"infinite" focus point.  In addition, the baffle for the EP needs to be of
some significant length in order to keep the stray light from getting into
the EP.
The lens can indeed be tested for quality against an artificial star set
several miles away from the telescope although that will be made more
complex as you will want to test over water from some altitude which may be
a bit difficult to find a place where you can see over a few mile stretch of
water and have an open window and be looking at something that also is a few
hundred feet in the air.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net


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