Re: Hour angle axis bump when declination axis stops


Howard Dutton
 

On Mon, Jan 20, 2020 at 04:57 AM, Howard Dutton wrote:
In this case the reason RA slows down early is that continued fast motion in RA would drive the 'scope close/under the horizon limit.  RA needs to slow down and wait until Dec is done than can start to move faster (and on to finish the slew.)
This isn't true.  After thinking about it and reviewing the horizon avoidance code (it's been years since that was written) really the algorithm slowing down RA is an artifact of the code not handling the sign of full range of Dec values.  This is by design, a simplification to allow operation in both hemispheres (northern and southern users.)  Working this way doesn't break anything per se, it does the intended job (of overall tending to keep the 'scope from dipping below the horizon limit,) just not as well as it could.  Since I'm here visiting this though I've changed the design of this bit of code in the master branch OnStep so it's "hemisphere aware" and behaves a bit more gracefully.  It now handles this test case better in that it slows the Dec axis instead of the RA axis which has a more pronounced effect on keeping the slew path away from the horizon limit.

Also, while I was at it I refactored some latitude code and improved the handling of its related values.

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