AutoStar #497 HANDBOX
Appendix C
54
The plot above tells you that the scope is not too well aligned.
Notice that the DEC guide corrections are not centered around
zero. This is because the object is drifting down in declination
due to the scope being poorly polar aligned. While the StarLock
is succeeding in tracking the star, you will get fi eld rotation over
time due to scope misalignment and may not be able to point to
targets near the poles. When you see this type of plot it is time to
drift align, or realign your scope.
If you see an RA histogram with two humps, you are
guiding too aggressively and need to reduce your
guide rate.
APPENDIX C:
Automatic Rate
Calibration (ARC - Polar
Mode Only)
Using StarLock’s Automatic Rate Calibration (ARC) Feature
Obtaining best performance from StarLocked telescopes requires
that the guiding aggressiveness be optimally set for current
viewing/imaging conditions. A guide rate calibration routine
has been included in the StarLock software that automatically
determines the best rate based on viewing conditions. Calibrating
your guide rate is a two-step process. First you will need to train
and update the mount’s Periodic Error Correction (PEC). Then
you will run the Automatic Rate Calibration (ARC) routine. If you
have already trained your mount’s PEC you may go directly to
running ARC.
Periodic Error Correction (PEC)
First set-up and align you scope. Now slew to a bright star near
the celestial equator. Using your AutoStar II handbox, press the
"
7/Ret
" key to bring up the
StarLock
menu and
Set RA Rate
and Set Dec Rate to
33%. Exit the StarLock menu by pressing
MODE. Wait for the StarLock light to come on continuously to
indicate that it has locked up on the star. At this point, simply
go the hand box menus and select
Setup/Telescope/RA PEC/
Train
and press
ENTER
. The StarLock will lock onto the current
star and watch it for one worm revolution, about 6.4 minutes, and
calibrate your drive’s PEC. For even better PEC training, add one
or more cycle’s worth of data. Select
Setup/Telescope/RA PEC/
Update
and the scope will then run one more 6.4 minute worm
revolution, refi ning the PEC.
PEC training will be retained in the telescope’s database and will
not require retraining providing that you use the “Park” routine
before turning the power off. The “Park” routine can be accessed
through the “Utilities” menu in AutoStarII. PEC is retained even
if you loosen the clutches, reposition the RA or DEC axis or
disassemble and reassemble the telescope. Realignment will be
required, but PEC training will not be required.
Automatic Rate Calibration (ARC)
Slew to a bright star near the celestial equator or you can use
the same star that was used to train PEC. Go to the StarLock
Menu by pressing the "7" key. Then scroll down to Auto Rate Cal.
The hand box will initially display Test Dec 33%. The percentage
value will change about once a minute while it evaluates different
rates. It will then display Test RA 33% and evaluate several rates.
Finally, the scope will beep indicating calibration is complete and
display the result on the hand box. Press the ENTER button to
continue.
If you need to abort automatic calibration, just press the mode
key. The process will stop and the default values will be used as
the guide rate.
When to use Automatic Rate Calibration (ARC)
ARC calibration should be repeated at the start of an imaging
session, if you have changed the optical tube assembly or if
environmental conditions have signifi cantly changed during an
imaging session.
