Re: ATM Yet another interesting thought

[Aplanatic@aol.com]

A while back I looked into using magnetics (voice coils plus rare-earth magnets) as actuators for a Cassegrain secondary.  The resistance of the voice coils and the weight of the magnets and mirror place very serious constraints on the bandwidth of the system.  As I recall, for a 5" diameter secondary, 1" thick, the available bandwidth was on the order of 10 Hz if one was willing to dissipate a couple of Watts, on average, in the coils.  The thermal dissipation can cause serious problems because the heat goes into the optical path unless it is actively removed.

A better approach, I think, is to use piezoelectric actuators.  The solvable problem with PZT material is the high voltages required to drive them effectively (up to 1K volt at tiny currents.)

Dave Rowe