Re: ATM vibrations...

["Bob May" <bobmay@nethere.com>]

>So, when I see vibrations in the eyepiece, they must be caused >by:
Are you talking theory here or reality?
Seeing a 1/4 arcsecond vibration isn't going to really affect your viewing
as the scope is going to be averaging out the vibrations (mass tends to do
things like this, especially when something slightly springy is in the
driveline like a thin rubber drivewheel) and thus, you will actually
probably see a fairly smooth motion.
I might add that doing the conversion to the eyepiece magnification just
shows how big the shift is going to be to the eyeball and, since that's a
fairly fixed value, you will be able to see whether you will actually see it
as a discrete motion.
Unless the scope resonates at or near the 66Hz frequency of the drive, the
motion will be a fairly damped one and it may be that you won't see anything
of any kind of stepping motion.  I might also note that the frequency of the
motion is well above the "fusion" frequency of the eyeball so you won't be
seeing the 66Hz directly but seeing some subharmonic of that frequency (you
pretty much need to get below about 24Hz) and that would problaby be either
22Hz (1/3 but probably not really visible), 16Hz (possibly seen) or lower
frequencies although anything that low would have to be assisted by
irregularities in the drive system to actually resonate.

Bob May
http://nav.to/bobmay
bobmay@nethere.com