From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


Didn't know that periscope lenses got that big! The lens will be a decent
to excellent lens for doing astro work.  It is a normal design lens used to
see things miles away and thus, it is pretty much designed to do the
infinite distance that we use for looking at the sky. The thing that is
really nice is that they are intended for visual use so the color
correction is more than good enough through the visual range for the
magnifications used in the periscope.  This may mean that the color may
still be there for much higher magnifications but I'd suspect that the
makers of the lenses did a decent job even then.  With an 86" FL, you
do have some ability to use short FL lenses and a 6mm will be about the
limit for good imaging which isn't that bad of an eyepiece as you can do a
12mm with a 2x barlow, something that should be in everybody's collection
of eyepieces.
A telephone pole a quarter to half mile away or so would be a good place to
get a glint of sunlight off of one of the insulators and that would be an
excellent source for an artifical star image. Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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