Hi 'PUGers,

I finally got a few minutes to test out the Matt Considine/Jim Burrows Lunar
GOTO program on a couple of 'scopes. This is going to be a neat tool for
touring and learning the moon.

I synced on the moon by centering its disk in a low-power eyepiece field
that was just larger than the diameter of the moon, and then WentTO the
crater Plato, chosen from the lllooonnngggg list of lunar features given
by Lunar GOTO (Plato is one of the few craters that I know by heart - it's
the huge dark one up north). Granted, the 30arcmin field was large, but,
darn it, it looked like LunarGOTO had put Plato smack in the middle of the
field on the first try.

So I said, "OK, I dare you to do that again", and I gave a command to GOTO
the crater Archimedes (just a bit to the south). Looking into the eyepiece,
I felt a queasy, sinking feeling in my gut as I stared at the anonymous
unrecognizable crater, NOT Archimedes, that was now nicely centered in the
field of view. God I hate beta testing.

The first step in sorting this out was to make sure I knew where Archimedes
is. I glanced over at the Rukl moon atlas. The bright, rayed crater that
I had intended to GOTO was actually Copernicus, not Archimedes. I have no
idea why I thought Copernicus was Archimedes - heliocentricity has nothing
to do with buoyancy, does it? Anyway, what was centered in the LX200 after
my command to GOTO Archimedes was, according to the Rukl diagram, Archimedes,
not Copernicus. The score was: Lunar GOTO 1, Rob zero. I installed the
necessary patch in my brain and carried on from there.

The story repeated itself with a second mistaken pair of craters, and I have
another brain patch. Lunar GOTO 2, Rob zero. After that, I couldn't trust
myself with any crater names. I did get the Sea of Tranquillity right, I
think - or at least, Lunar GOTO, Rukl and I all agree on it.

Lunar GOTO and Rukl make the moon a more interesting place to explore.
But I have to say, I had to give up on the standard star diagonal and instead
use a non-reversing 45 degree diagonal. The 45 degree angle is a bit of a
pain, but much less painful than trying to compare non-reversed Rukl charts
with the reversed images seen with the standard diagonal.

It seems that the 57.9 Hz tracking frequency recommended in the user manual
for lunar work must be an average that is not always optimal. I found that
the scope drifted away from the chosen lunar feature after a few minutes,
but it would re-center the feature if I hit GOTO again. The orbital elements
for the moon that are stored in the lx200 database are accurate, but the
57.9 Hz tracking rate is not (at least, it's not accurate for the current
orbital position of the moon). Also, I guess the best results with Lunar GOTO
will require PEC training, since the periodic error (in my scope) is
substantial
compared to the relatively small angular distances between any two lunar
features.
Lunar GOTO does require that the lx200 drives in a person's scope be
up-to-specs,
of course, since lunar features are all less than 30 arcmin apart, and sometimes
less than the 1-arcmin GOTO accuracy specification for the lx200. If a scope
has out-of-spec. slop or backlash for any reason, Lunar GOTO would make the
error
stand out clearly.

Rob Preston
Pgh PA

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