Re: [ATM] Aero Ektar Coma Corrector?

[Jarvis Krumbein <jkoptic@juno.com>]

Mike, the 7" f2.5 Aero-Ektar once was one of the favored lenses for astro
photography.  It was readily available in the surplus market at a
reasonable price.  Henry E. Paul considered it an ideal beginners lens in
his "Outer Space Photography for the Amateur" which was published in
1960.  Since the lens was designed for black and white aero photography,
it left something to be desired when used for astro stuff.  Paul noted
that spherical aberration cleared at about f3.5, coma at about f4 and the
best all around stop at f5.6.  This would cover a 4 X 5 film except for
the corners.  With todays fast films, stopping down to f5.6 should
produce reasonable exposure times.  If you want a lens faster than f5.6,
the Aero-Ektar is not the choice nor would a coma corrector be be easy to
design much less fabricate.  

Learn to live with it.

Jarvis Krumbein

On Tue, 25 Jan 2005 07:46:24 +0930 "M/S Heald" <maheald@octa4.net.au>
writes:
> Hello!  I have a 178mm aero ektar that I have to stop down from f2.5 
> to f5.6
> because of coma before getting sharp 4x5 wide field shots.  Is it 
> possible
> to design a coma corrector so that I can use it at f4 or f2.5?  
> Best
> regards.
> 
>  
> 
> Mike
> 
> 
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