Tips for Training Your LX 200 GPS Telescope In Polar Mode



After working with several folks and hearing of woes when attempting a good
"Train Drives" via polar mode, I thought I would post some tips for very
effective training for those using the LX 200 GPs scopes in Polar mode. I
have run tests for about a month now on virtually the entire line of Meade
scopes and have found these following to be the key to excellent and
near-perfect GO TO's from precise polar training.

1) Do not expect your telescope to have good GO TO's if you have not trained
both drives, no matter in alt-az or Polar mode;

2) Polar Training on a star does NOT work well, if at all, on versions prior
to v1.6b; although polar training can be done in 1.6a and 1.5 versions, your
target star will drift appreciably, thereby affecting results;

3) Training on a star in polar mode must be done as rapidly (but
correctly...) as possible. The longer that YOU take to train, the worse your
residual error will be. I have seen train errors as much as 7 arc minutes
and as little as 0.5' arc with delays from 12 minutes to five minutes,
respectively. The more rapid you can precisely train, the less drift there
will be in your target star. Ideally there should be NO drift, but this is
not the case...because of sidereal motion and the lash effectivity motion of
the telescope during training there WILL be an offset over a given period of
time...the longer the, the larger the residual and the less effective is
your training;

4) Training of course must be done at high magnification, and by all means
with a crosshair eyepiece; "guesstimating" true center is a very difficult
thing to do and takes up valuable time (see "3" above); USE your
finderscope to start training...it will speed up the process and will almost
guarantee that you will NOT overshoot your target star...remember that if
you do overshoot, you must start over with your Train Drive sequence....you
cannot go backwards; I have found that when the telescope moves its offset
away from your target star, frequently the distance is so great that you may
become distracted by the time the star finally makes it back toward center,
or you might choose a speed much to fast for accurate training. Try using
speed "5" and the finder to first get the star close....then change to speed
"2" and move back to your eyepiece for final and precise training;

5) Only stars within one hour (15 degrees roughly) east or west of the
Meridian should be selected for good training in Polar and your star should
be as close to possible with the Celestial Equator, or not more than 5-8
degrees north or south of "0 degrees declination;"

6) It is unlikely that you have done a good (or any)PEC prior to Train
Drives; if you have, then turn PEC "off" to train;

7) For polar mode, you do NOT need the home sensors on....turn them "off" as
well and leave them off for subsequent operation.

Best of luck....I think this will help some of you having trouble in Polar
Mode. Using these tips, I have been able to achieve dead center GO TO's on
nearly every telescope that I have used so trained. So close that I can do
a selected comet GO TO, begin imaging as soon as the telescope stops, and
have the object within 1-2' of dead center when the image is finished.

Dr. Clay
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[email protected]
Arkansas Sky Observatory
Harvard/MPC H43 (Conway)
Harvard/MPC H41 (Petit Jean Mountain)
http://www.arksky.org/

Copyright Arkansas Sky Observatory 2003  [A.S.O.] All rights reserved. Revised: