Gday Baz/Alan
Just a quick few comments.
Querying the scope too often is not "normally" very useful, as at a max, the 497 type handboxes only read the encoders 10x per sec.
The LX200GPs can extend this out to 0.33x per second if polar.
Also, if polar, the 497s rs232 responses for Alt and Az Lie
as they dont do a proper conversion, they return "base relative" encoder vars.
On top of that, the firmware also stores a secondary set of dummy variable "copies" of RA/DEC/Alt/AZ as they go, and use these at times to respond to serial commands.
Depending on whats going on in the background, these may not get updated as often as they should be
Ie treat the results with a grain of salt
Andrew