Re: [ATM] Gimbaled Secondary mirror

[Aplanatic@aol.com]

Thanks, Jack, that's an important relationship to know. 
 
Regarding gimbals:
 
Are there two or three actuators?  What is the total travel of the  actuator?
 
Is it true that three actuators are always needed in order not to produce  
focus shift when doing tip-tilt?  I was going to suggest a two-axis  compliant 
hinge until I realized that three actuators may always be  necessary.
 
-- Dave
 
In a message dated 6/30/2005 4:05:49 P.M. Pacific Daylight Time,  
atm@hudler.org writes:

Further  research on the Wetherell and Rimmer, turn up several derivatives,
one in  particular; Cassegrain telescopes: limits of secondary movement
in  secondary focusing by Roger N. Clark which concludes;

The maximum  distance to which the secondary mirror can be moved with
respect to its  primary in a true Cassegrain telescope with limited 
image deterioration is  found to be proportional to the fourth power of
the focal ratio of the  primary mirror. This limit is independent of all
other parameters  describing the system when the magnification of the
secondary is greater  than about 3.

This is perfect because our secondary is "greater than  about 3", well 2.997
buts that's about 3 :)

Jack

Gimbals  anyone?


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