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LX200R Slewing -  Software Routine Testing

Previous VB software routines for commanding telescope slews and imaging of targets have encountered problems when used with new LX200R telescope, whereby the scope was either still moving or not fully stabilised before imaging commenced. 

Using old LX200 classic,  calls to the TheSky routine  "Telescope.SlewToRaDec" would not 'return' execution to the next program line until after the slew had completely finished (i.e. telescope slews were synchronous (that is, program execution stops until the slew is complete). 

However with my new LX200R with its LX200GPS mount it evident that calls to .SlewToRaDec do not stop program execution during the slew, but immediately continue with the next program line.  If telescope slews have somehow become asynchronous (don't understand what has changed to cause this) then it should be possible to use "Telescope.IsSlewComplete" command to see when the telescope slew has finished.   However this routine simply returns 1 saying that the slew is complete, even when it is obvious that the scope is still slewing.

As a temporary workaround the length of the Post-Slew delay (normally 3 secs) has been extended to 17 sec and then used twice (for a total of 34 secs delay) before imaging commences.  It general this allows enough time for the slew to be completed.  However for short slews the delay is too long (wasting session time), whilst for very long slews the delay is still quite long enough. (Note the max slew speed for LX200R is set to x arc deg/sec to help protect the motor/gears]

After a few attempted trials a new routine has eventually been written that loops around until it recognizes the end of a slew. It does this by spotting when the telescope's position is no longer moving, because it has not moved by more than a set amount (0.1 arc min) within a set interval of time (2 secs).   Trials during this session show that this new routine was able to successfully take non-trailed images without introducing unnecessary delays.

Taking information from the script's log file and status reports allows a graph to be compiled showing slew time against slew distance. (see below), TYhe graph shows both a) generally increasing slew time with slew distance and b) significant variation in slew time for similar slew distances (see the slew time variation associated with very short (<1 arc deg) slews,  used whilst acquiring  3x3 Mosaic.

In order to work successfully it seemed necessary to the set the cross-hair update frequency to be less than the time interval between scope position checks. Furthermore the timeout interval for the routine needs to be set to 60 secs, not the 30 sec used during the trial.

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