[ATM] Re: Banishing the secondar]

[Mark Holm <mdholm@telerama.com>]

Looks like Dave has taken the tack of raising the f-number to reduce 
coma and astigmatism.  This possibility is always inherent in the 
schiefspiegler design.  Anton Kutter kept his larger 2 mirror, 1 lens 
schiefs to about f/20.  The Kutter - Knab 4.25", 2 mirror schief is at f/27.

Possibly, with modern optimizing software, Dave has been able to tweak 
the angles for slightly better cancellation of astigmatism and coma than 
was possible with the analytical methods available to Kutter.

Dave,

I would like to see your design numbers.


A German, Dr.-Ing. Georg Dittié,  has invented a schiefspiegler, using 
two tilted meniscus lenses, that appears to have significantly improved 
performance over the two mirror, one lens schiefs.  He mentions pursuing 
patent rights, but there is no mention of an actual patent application 
or issued patent.  Dr Dittié runs an engineering and manufacturing 
business, so he is probably quite well versed in the practicalities of 
patent applications.  He may well have carried through on his intentions.

One could always enquire.  It might help to be able to read and write 
German.  Despite the best efforts of Professors Gerlach and Friedlander, 
I am not able to do that to any significant degree.

Here are the links

http://www.videoastronomy.org/schiefspiegler/kutter.htm

http://www.videoastronomy.org/

Mark Holm
mdholm@telerama.com



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