At 15:05 2001-07-04 -0500, Eugene Lanning wrote:

>So, is the poor GOTO accuracy a wear/aging problem or a failure induced
>problem?

After a year or so playing with Meade's 2-star altaz alignment, my put is
it's neither: GOTO accuracy is built-in - the alignment algorithm and the
mechanical construction. Thoughts (accuracy estimates, scope-dependent,
are for my 8"f/6.3):

1) PLOTLX is a program which contains, and tries to correct, gear errors
(runout & radius error). This desynchronizes laptop & keypad. Whole sky
accuracy ca. 1'. Other misalignment errors are estimated by a real-time
Kalman filter; the gear errors were estimated once by centering a large
number of stars (a la Xpoint (?)).

2) PLOTLX0 does not correct for gear errors, so keypad tracks
laptop. This is essentially the same as Meade 2-star altaz alignment except:
a) Any stars in catalog can be used,
b) n-star alignment can be used, but it only improves Meade
alignment by a factor of 2 ~ 2' accuracy.

3) To correct gear errors (PLOTLX) it is necessary to "home" the gears -
mark on dec gear opposite the hole in the cover & red mark on RA gear
opposite the 45 deg cut in housing.
a) To avoid having to check the gear home position, return the
telescope to S & level at end of session.

4) For maximum accuracy, the bubble must be inside the black circle and
the azimuth should be a close to south as possible. At home:
a) Rough level tripod on the pad using torpedo level and moving
the tripod legs laterally.
c) Lock down telescope and do fine leveling.
d) Return to S & level (at 1.5 deg on DEC circle) before turning
on the scope.

5) Backlash-aware centering. Selecting a star on the laptop gives
directions for final centering movements in CENTER & GUIDE.

6) BESTPAIR selects best pair of stars for Meade 2-star altaz
alignment. Have EVALALGN.EXE (Ada code) in the same directory.

7) Last, but not least, check the scope's time and position (if you've
moved to/from dark sky site) and use the reticle EP.

-- Jim Burrows phone 206.244.2933, fax .0294
-- http://www.halcyon.com/burrjaw
-- Seattle N47.47233, W122.36620 (WGS84)

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