Center without sync'ing or nudging


#1

I have mentioned this request but I don’t think I entered it as a feature request.

My cge-pro does not land exactly where it is told to - but it does reliably land a bit off from the target. This means that repeated solves/syncs/slews will not converget to the target and I can’t center reliably. I need to do it manually - particularly to place a guidestar on oag.

Other mounts are not designed to sync all over the place - so for them a sync should be avoided.

And other mounts seem to have similar unknown problems that cause them not to converge to the target after multiple iterations.

I think many of these problems would go away by not doing a sync at all - but instead have SGP keep track of the error when converging on a target - and keep adjusting that error on repeated solves/slews. Essentially sgp would calculate its own sync offset when centering a target. There would be no need to keep track of this offset because whenever you start the centering process you set it to zero - and it only exists as you converge on the target during the centering process iterations.

This would mean the initial slew to a target might be a bit off since it doesn’t benefit from a sync - but at the same time if you sync in one part of the sky and then go to another - the sync may be detrimental to accuracy and you would want to unsync before you did the long slew. Additionally - if someone does want to sync - they can always do it manually near the target.

The basic idea is to have an error vector E, in ra/dec, that is initially (0,0). You slew to the target, T, plus the error, E: SlewTo(T+E). Then you solve and find the new error of the target from the new position, P: dE=T-P. Then you adjust E with E = E + dE. Then you repeat and slew to T+E.

As long as the slews are repeatable this should work. And it avoids sync, and should handle many unknown errors that currently prevent mounts from centering accurately.

Frank


Error on Centering has grown significantly

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