Hi Chris
On (16 Sep 96) Chris Harper wrote to Alec Cameron...
 CH> I intend on having all the mirror clusters drives linked, and use a 
single
 CH> sensor/drive mechanism for each axis of control. The sensor will feed a
 CH> small z-80 computer which will control the locking stepping motors I use
 CH> to drive each axis.
Smart move, it is a job for a computer. You might get a ready made program as
used for astronomical telescope drives.
 CH> This should give very precise mirror alignment without to much power
 CH> consumption from constant drive adjustments. The frequency of the
 CH> adjustments will be controlled by the sensitivity of the sensor, which
 CH> will be mounted on one of the mirror clustors.
Wind loads a problem? A big stationary mirror is one thing but you will need
rotational freedom in two planes, could be a floppy setup. As an alternative
to having the steppers work to a pre- programmed cycle, you could consider a
continuous auto- finder as used in some OZ solar panels. These are sun
seekers, the azimuth and bearing of the sun is measured then the drive
motors respond.
Hey I am an innocent bystander repeating learned info [newspapers, mags] of
Long Ago. One of the "Chairborn Division".
Of course, the focal point
 CH> will move more when the sensor isn't set real sensitive. All I need to 
o
 CH> is find a "sweet spot" in the setting, where the movement isn't to 
reat,
 CH> yet there is a fair interval between movements.
Murphy's Law of sweet spots- these move about a lot, and within an hour of
making final adjustment.  Cheers......ALEC
... Life is one long process of getting tired
--- PPoint 1.92
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