Re: APPM Model sanity check (suggestion)

John Upton


   I also set up anew each night (for the most part). I understand exactly your concerns with using an old model. I have not tried it out yet but think I will try this soon -- the night or two.
  • Build a small (normal for me) model of maybe 30 to 50 points. 
  • Use that model for the evening.

  • Next night, enable the previous 30-50 point model's pointing and tracking corrections and recal at the zenith or maybe at the intersection of the celestial equator and meridian.
  • Create and run a new "tiny model" of 9 points (Zenith and 4 East and West).
  • Do not install the new 9 point model.
  • Check the APPM reported errors for each point in the new model.
  • If they are all less than about 1-2 arc-minutes (or other criteria), discard the 9 point model and use the previous recal'ed 30-50 point model.
  • If there are larger errors in the "check (9) point model", go ahead and run a new full model.
   The intent for me is to run a new model while the previous one is active. (This assumes the old model is activated / enabled and a recal has been done.) Hopefully, the recal'ed old model should have accounted for orthogonality errors and differences in polar alignment. The new 9 point run is a way of checking how much difference there is between the old and new models.

   Does anyone do anything like this? Will it work? I do plan to try it out and see for myself. I expect the downsides to be differences in temperature and air pressure from night to night but I assume those differences are also present if you have a permanent set-up.


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