Re: [ATM] The camera obscura

[Michael Lindner <mikell@optonline.net>]

On Wednesday 25 August 2004 11:13 am, Lock,Tony [Dartmouth] wrote:
> 	3.  I would need a lens of 4" to 6" aperture and perhaps 10 feet
> focal length

D&G Optical advertises 5" through 12" achromats at f/12 to f/30 at 
http://www.dgoptical.com/objective.htm

> 	4.  I would need an 8" flat of reasonable quality

Diagonals of 6" and more are available commercially at Newport 
(http://www.newportglass.com/appxdiag.htm) and other places. If your lens is 
6", the diagonal probably doesn't have to be much bigger (in fact, if you put 
the lens before the diagonal, the diagonal can be smaller than 6").

Either way, I'd recommend an optical window in front of the first element to 
protect it from the elements (pun intended). You could either grind regular 
window glass for that or get a thin water white plate glass blank from 
Newport (http://www.newportglass.com/acorretr.htm) or other vendors...BTW 
Newport's catalog is at http://www.newportglass.com/angwcat.htm

This isn't intended to discourage you from making a lens or flat, but if you 
choose to buy, the parts are out there.

BTW, I'm not recommending these as the vendors you should use or not use, 
these were the first Google came up with.

Clear skies...
-- 
Michael Lindner
http://www.starastronomy.org *** http://home.att.net/~mikel
http://www.atmsite.org *** http://www.atmlist.net

_______________________________________________
ATM mailing list http://www.atmlist.net/