Re: ATM quickcam Autoguider

[andydtg@phoenix.net]

Don Clement wrote:

>       I built an autoguider based on a United Detector four quadrant Silicon
>photo diode. The diode tracked the centroid of the star without using beam
>splitter, knife-edges ,or multiple detectors. The output signal processing
>was all analog, done with op amps, so a computer was not needed. The main
>drawback was sensitivity, it took a really bright star to work. In
>retrospect, perhaps the problem was the same as with CCD detectors, that is
>dark current. If I would have cooled the photo diode to -30 C perhaps it
>would be more sensitive. Well it might be worth digging up the old
>circuitry and cooling the diode with a Peltier cooler.

I wonder if using an image intensifier in front of the quad cell would
work, just put it in contact with the output faceplate. Input face at focus
of guide optics, with maybe a beamsplitter/eyepiece to find guide stars.
Surplus & Russian im int tubes are pretty cheap nowadays.

Another thought I've had is intensified video with a monitor & movable quad cell
looking at the monitor thru a small lens, just move it to a star on the screen.

Advantages are *fast* response, no cooling, & no computing power required,
just op amps & maybe relays as Don mentions.




Andy Saulietis / DTG Alt-Az-Fp Drive Systems
HDPE Worm Gears, Custom designs & Machine work
12617 Harriet Ln
Santa Fe, TX 77510 USA
409-925-8854 Voice/Fax
e-mail: andydtg@phoenix.net