The Gemini System was
developed mostly by
and Scott Losmandy.
For visual use all
you have to do is level the mount and point it to the North Star, by
sighting through the RA shaft. With proper selection, a good
pointing model can be created with only about seven stars.
After that, you can expect to spend the evening observing objects
instead of mostly just trying to find them.
alignment and pointing model creation requires a bit more work.
After leveling the mount I use a polar scope for the initial
alignment. Then I create a pointing model with about seven
stars, using my ccd camera. Because I only image to the west,
I never include any stars to the east.
If the Gemini
indicates that I am greater that one arc minute from the pole I use
the "Polar Axis Correction" (PAC) function to adjust the altitude
and azimuth settings. Then I create a new pointing model.
If Gemini still indicates an error greater than one arc minute, one
more PAC followed by another model creation will do the job.
I find this degree
of alignment more that adequate for 20 minute exposures with a 1600
mm focal length using the ST-7 ccd camera. When I get a camera
with a larger chip, better alignment may be required to prevent
It's a great
convenience to go the scope two weeks later, roll off the shed, do a
warm re-start, sync on one star and everything is aligned and ready
to go. Set up time is often as short as 15 to 20 minutes.