Re: [APML]: Meade LX200 Scope and ST4 Autoguider

[Chuck Vaughn <aa6g@aa6g.org>]

James T Waters wrote:

>      I was told by a local astronomy club member that the ST4 has problems
>      working with the LX200 scopes due to the way Meade designed the DEC
>      drive system.  The backlash for the DEC axis is about 3 seconds and is
>      not constant.

Are you talking about backlash or just delay in reversing directions? 
What I've always understood backlash to be was like tuning an old 
mechanical radio dial in one direction, letting go of the dial and
it slightly went in the opposite direction by itself. I sure hope the
LX200
doesn't have this problem. No guider could compensate for that. I would
think that a mount with dec backlash would be totally useless for
astrophotography.

If you're talking about a delay of up to 3 seconds in reversing
directions
then that's another story. Many mounts exhibit a delay in reversing dec 
direction but 3 seconds is a lot. Some of this delay can be caused by
poor balancing. Running the dec in one direction will cause it to load
up
and then have to unload before it can reverse adding to any play there
may be in the dec drive.

If you have good polar alignment some reversal delay should not be a big
deal as most dec corrections the ST-4 makes will be to try to follow
seeing
and not true dec drift. Any true dec drift will be guided out in the
long
run and not adversely affect your photo.

Chuck Vaughn  <aa6g@aa6g.org>