Re: [APML]: reducer lens for GEG

["Bobby Middleton" <bobbym@unicomp.net>]

The Astro-Photography Mailing List
------------------------------------

Thanks Dan. On my page I describe the different f-ratios of the
GEG as f11, f8, f7, and f/6. Those are the actual focal lengths I
have with my scope. I know this because I have calculated it
from comparing my photos with the star charts in the program 
Megastar. Philip Perkins has done the same and come up with 
focal lengths close to mine. BTW, he has a great article on using a GEG
with a 10" LX200 at http://www.astrocruise.com .   
Lumicon gives advertised f ratios for the GEG as f10 (straight-through),
F6.3 (lens in rear position), f5.5 ( lens in front ), and f4 ( lens in
front
with a 2" extension ). Lumicon sells the extension tube which gets
the camera a little further back and produces a f ratio of f4.  
I suppose that different scopes might produce different results
with the GEG in regards to focal lengths so I don't want to say
they are trying to mis-lead anybody with their specified ratios. 
Bobby Middleton

astropics at: http://home.unicomp.net/~bobbym/astro1.htm


----------
> From: Dan Medley 
According to the information provided, that
> gives me f/6.5 for in front of the pick-off mirror, and f/5 for behind
the
> mirror.  Am I missing something?