Re: ATM Lenses for finders?

[Bob Lombardi <blombard@iu.net>]

>
>Date: Fri, 2 May 1997 22:42:31 -0700 (PDT)
>From: Bruce Swayze <swayze@europa.com>
>Subject: ATM Lenses for finders?
>
>I want to make a homemade visual finder.
>
>Has anyone else been as frustrated as I am trying to find lenses to make a
>homemade finder?  
>
>I'm looking for something in the 60mm to 80mm size, with a focal length
>appropriately short for a low power finder.  An achromatic doublet would be
>perfect.  I've tried the Surplus Shack, but are there any other places to
>buy lenses?  Preferably used or salvage, or low cost.  But new ones would be
>okay if they aren't too expensive.  The whole idea here is to save some money.
>
>Another alternative would be to find broken or damaged binoculars, to
>salvage the lenses.  Is there a source for these anywhere?
>
>Any help would be greatly appreciated.
>
>Bruce Swayze
>swayze@europa.com
>

I've made a couple of finders in this size range from photocopier lenses.
The best one is about 80mm and 8" FL, so that a 25 mm ep yields an 8x80
finder.  Even in my suburban location, I can spot most of the M objects in
it.  This is a Zeiss lens that I bought from an electronic surplus seller
several years ago. 

The disadvantage is that copier lenses are mounted in metal cells, and are
heavier than bare achromats.  They usually have several elements, too,
rather than just a simple achromat.  All the surplus places seem to sell
copier lenses.  Some are better than others, but the ones I've tried made
decent finders, and I didn't really look for any specific brand.


Bob


Bob Lombardi            WB4EHS in Melbourne, FL                   \---\---\
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