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Hi Frank:
I don't see any expert replies to your questions so
I'll chime in with some nonexpert ones <G>:
1. The mode button was put in for some functions
that were never implemented by SBIG but as far as I know, its only function
now is to permit you to recapture a guidestar after halting guiding for a short
time. I believe you hold down the mode and track buttons simultaneously.
Matt and others have remarked on this and it's in the archives
somewhere.
2. The A numbers indicate the sum of the x and y
errors in the last interval, adjusted in some algebraic way. The higher the
number, the greater the correction applied (ie, the worse the tracking). AE just
means that the error exceeded 9, so it's worse than A9. For most work, any A
value greater than 4 means you're in trouble, but this is also a function of
focal length, so at very short focal lengths (eg, piggybacking a 100 mm lens on
a camera), you could probably get away with A5s and A6s.
3. The readings *during* the calibration are the
brightness value and X and Y pixel positions achieved by the ST-4 applying X and
Y relay closings for the C1 and C2 calibrate times that you have set in the menu
(or just left at their default values). E numbers after the calibration finishes
are error codes. I believe the different numbers can be decoded to tell you what
particular error occurred (maybe in the manual?), but I never pay any attention
to the specific number, I just try to find a better guide star or center it
better on the chip and repeat the calibration. Any E number after a calibrate
means calibration has failed and you need to repeat it. If calibration is
successful, you just get a "Hello" at the end of the calibration.
Regarding focus with an OAG: the focal point via
the off axis guiding port is remarkably far from the optical axis for
the 2 systems I have used. I find I need at least 1.5 inches of extension tube
in the OAG guiding port to hold the ST-4 far enough away to get it into focus.
Lumicon and others carry these extension tubes in various lengths.
Hope this helps and wasn't too
obvious....
Bert
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