Quote:
Originally Posted by frolinmod
If anyone here is having great success with doing a short re-calibration run to an existing model instead of full calibration to create a new model, please pipe up!
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Since the mathematics are rigorous, that is, they work both in theory and in
practice, it means that some of the terms in the model that you obtained from
the long sampling run should not be held fixed for the short sampling run.
For a fixed observatory, you will need to re-compute at least ID and IH and should
possibly consider CH as well if you have changed anything, such as re-attaching
a camera or rotating it in the holder.
A converse way of saying this is that something in your setup is likely to have
changed between sessions or you have an unsystematic random error somewhere.
A sudden mirror flop is a good example of an unsystematic error and no pointing
analysis system can model a random error.
If you do multiple long sampling runs of approximately the same number of stars distributed
across the entire sky and compare the magnitude and sign of each of the terms along with
their associated standard deviations, with the exception of ID and IH, they should all be very nearly the
same.
Few things throw out a pointing model more than a single outlier. Automated sampling can easily
misidentify a star particularly if not guided by an existing reasonable model.