From: "Pete Newman"
Subject: RE: 2.5m obslog 20040825 (MJD 53243)
Date: Thu, 26 Aug 2004 13:06:59 -0500
Scot reported:
> 10:13Z at frame 120, mu=45 at the rotator error is around -0.084; ex
> expected this since we are at an altitude near 87 degrees and are probably
> tracking very fast - we can't tell how fast since stripeAxisRates
> doesn't work.
Just a reminder that we don't know the sensible altitude limit for the current
combination of azimuth axis tilt and pointing model, which is due to be
changed again during bright time.  I think this is by far the closest to
zenith we've been with this combination.
But I'm just a little confused.  The skippy table includes:
===============================
---=== SKIPPY RESULTS ===---
Run  Frame nFrames stars muErr   muRms   nuErr   nuRms rot      az    el
---------------------------------------------------------------------------
 4800    86   5     78  -7.400   0.155   3.100   0.225  0.03843  162   81
 4800    96   5     85  -7.500   0.168   3.500   0.209  0.05256  168   83
 4800   111   5     77  -5.800   0.157   4.300   0.329  0.08047  182   85
 4800   131   4    116  -3.100   0.513   6.200   0.700  0.02765  230   87
 4800   183   4    154  -0.800   0.172   6.500   0.175 -0.05684  309   81
===============================
Note that the worst rot error is _not_ at the highest altitude, and quite
dramatically flips sign on the way down.  The ltMatch results are similar.
I'm hoping someone who can think through the spherical trig in their head will
say, "That's just the errors in the az tilt and pointing model, too," but I
thought it worth highlighting, given this is the first (and last!) night of
imaging since the summer shut-down.
Cheers,
--Pete
(ps.  What a heroic shake-up, guys!)