Re: [guide-user] LX-200 pointing trouble

Bill J Gray Feb 28, 2004

Hi Lawrence,

Hmmmm... just how much error are we looking at here? A few arcminutes?
Dozens? Degrees? I assume the error is repeatable (i.e., go from one
part of the sky to another and back again, and it's still off in the
same direction by the same amount)? Any clues other than "it's off"?

You mention that you don't get good results with the synch operation:
do things get worse? Better? Exactly the same? Still bad, but in
a different direction?

One possible source of trouble is in the epoch used by LX-200 scopes.
I've been unable to find information about this, and it hasn't mattered
much in the past; we've been close enough to J2000 that the difference
would be less than the usual pointing error in the scopes. Guide assumes
that the RA/dec sent to or received from the scope ought to be in the
epoch of date. If I'm wrong, then you should hit Alt-J and enter

SCOPE_EPOCH=2000

This will adjust the coordinates sent to the scope by up to a few
arcminutes. I'd be _very_ interested to hear from anyone who tries this
out. The above capability was originally added mostly for folks with
home-brew LX-200 clones who needed an adjustable epoch... but it could
be that my assumptions about the epoch used in LX-200s have been wrong!

-- Bill