Re: [ATM] Worm mounting

["Don Clement" <clement.focuser@verizon.net>]

This topic has digressed away (audio amplifiers) from what I was trying to
say about using the most linear drive components to start with. The closed
loop BW and slew rate of telescope drives is extremely low due to large
mechanical mass and the very slow
response of CCD detectors in the negative feedback loop (guiding). Almost
any
transient will be fast enough to overwhelm the negative feedback loop and
cause unwanted intermodulation products from nonlinear component of the
drive system. Linear components do not produce modulation products. That is
why I like the cable drive…it can be made to be extremely smooth and linear.
So when the negative feedback (guiding) fails to compensate for internal or
externally generated transients then at least more intermodulation products
(artifacts) are not introduced into the final image by nonlinear drive
components. Some have increased the negative feedback BW and slew rate by
using so called “adaptive optics” or a lightweight tip-tilt mirror near the
focal plane. This can increase the feedback BW and slew rate, but are still
limited by slow responding ccd sensors in the negative feedback loop.


Don Clement

Running Springs, California



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