Re: [ATM] Finally !

[Woodchuck <djv@bedford.net>]

On Fri, 30 Sep 2005, Saqib Sajjad wrote:

> hello all,
>
>
> finally i have been successful in getting an optically
> true 4" concave mirror.its focal length is 1828
> milimeter (72 inches). i am planning to use 1 inch
> secondary (house hold mirror). tube(pvc pipe) is
> around 5 inch in diameter with 2mm thickness. eyepiece
> will be 30mm (binocular's). is there anything i
> should/shouldnt be using.any suggestion from everyone
> is welcome !
>
> Saqib

The second-surface mirror may produce double images.  Better to use
an optically flat first-surface mirror or a prism.  If you've gotten
the eyepiece from a conventional ("Zeiss") design binocular, you
may have four suitable prisms at your disposal as well.  Sometimes
binoculars use front surface mirrors in place of prisms, so much
the better if that is your case.  Compact binocular designs (many
modern ones) do not use the older method of twin 90 degree prisms
to erect the image, using some other method.  The old Zeiss design
separates the objectives quite a bit, giving the characteristic
stepped "binocular" appearance.

The use of a prism to bend the optical axis to the eyepiece in
the Newtonian design is not fashionable at present.

Dave
-- 
        In each of us, there burns a soul of a woodchuck.
        In every generation a few are chosen to prove it.

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