Re: [ATM] Tracking Systems for Astrophotography

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

The TV remote sensors work on AC rather than DC for the signal.  In other
words, it doesn't matter how much light there is, you autobias the detector
electronics so that you are in the middle of the range and then look for the
signal from the remote which is a series of pulses.  Generally the system is
looking for a pulse stream in the high KHz or MHz range which makes the
whole job easy.  All of the temp effects of silicon conductivity become
irrevelant when you have this ability.  You can chop the light from the star
and get this effect if so desired and that will definitely improve the
ability to see a bit of light in the presence of a lot of DC bias from the
temp.  This process was what was used in the early days of op-amps (back
when they were made from tubes) to be able to amplify small DC signals.  In
that case, the input signal was impressed across a transformer after being
switched by a DPDT relay, the AC signal then amplified and rectified to
return back to the DC signal only amplified.  Needless to say, Nyquist
limits left the AC component of the signal to fairly low frequency limits
but most applications in those days were fairly low frequency applications
anyway.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net


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