ATMing in the September Sky & Telescope

["Gerd F. Herzogenrath" <gfh@fh-furtwangen.de>]

Gary Seronik wrote:
> 
> Hi Dan:
> 
> At 01:02 PM 7/18/1999 +0100, Daniel Fundo wrote:
> >
> >Gary,  I have heard of the Mersenne design before, but I thought it was
> >an afocal Cassegrain arrangement.
> 
> It can be, but Clyde has done something quite interesting. Using a pair of
> flats, he sends the light out the side of the scope along the altitude axis
> and into a refractor.  With his arrangement, the eyepiece's altitude
> position is stationary.  It's a joy to use.  You simply sit in the chair
> and observe - very comfortable.
> 
> Gary


Hello,

this arrangement is called a Nasmyth focus, first used by James Nasmyth
in the 19th century and named after him accordingly. Also in use on many
professional telescopes today. Nasmyth telescope was a standard
Cassegrainian, not a Mersenne design.

Regards, Gerd