----- Original Message -----
Sent: Wednesday, July 17, 2002 1:08
PM
Subject: Re: [APML] Couple more ST-4
questions
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
----- Original Message -----
Sent: Tuesday, July 16, 2002 11:42
PM
Subject: [APML] Couple more ST-4
questions
Thanks to the help of many of you, I was able
to successfully (I think) guide some shots tonight. Now, if someone
could explain a few things to me, I'd really appreciate it. 1) What
does the mode button do? 2) While guiding, what do those figures
mean? I know a few (I think), but some don't make any sense, and the
manual doesn't go into too much detail. For instance, A=. -0 5
The A= sometimes reads any of the following: A1, A2, A3, A4...A8,AE,
and A=. (do they represent adjustments?) They seem to go
sequentially- up or down, but not always. The . (dot), I believe
indicates that a relay is engaged. Then the two numbers are the
corrections in x,y (right?). 3) When you do a calibration, what do the
readings it produces mean? For instance, after the calibration ran, it
showed this: E1 4 (then 3), E2 3 (then 4). Do these
numbers mean anything to me?
One last question... I got a bit overzealous,
and hooked up the GEG, and tried to guide off-axis. I found that no
matter what I did, I couldn't get it in focus (in f/6.3 mode). I tried
the extension tube, and the best I could get was almost in focus with the
extension tube literally hanging on by a millimeter, and the ST4 the
same. I could never get it completely in focus. I double-checked
the placement of the lens, even tried using a prism before the ST4 head, and
tried a camera extension. No luck. Any ideas? My setup is
a 10" LX200, GEG, ST4, Nikon F2.
Any help is appreciated.
Thanks,
Frank