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Pointing Model

I consider data from two sets of nights: Dec 6-9 and Dec 16-18 (dates are for the beginning of the night).
The left plot shows the pointing errors, drawn as line segments as a function of Hour Angle and Declination.
The red symbol is the location given by TELRA, TELDEC; the line segment points to the true telescope pointing
as determined from matching the exposure to the NOMAD catalog. I have subtracted off an overall constant
offset in each coordinate in order to make the patterns stand out more clearly.

I fit a simple pointing model to the errors in RA and DEC:

err(RA or DEC) = a + b*HA + c*DEC

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December 6-9, 2012

Ignoring the constant terms (which I haven't preserved exactly), the slopes are:
RA: b = 1.031 arcsec/deg, c = -0.505 arcsec/deg.
DEC: b = -0.033 arcsec/deg, c = -1.203 arcsec/deg.

RMS residuals: 7 arcsec

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December 16-18, 2012

Ignoring the constant terms (which I haven't preserved exactly), the slopes are:
RA: b = 1.060 arcsec/deg, c = -0.710 arcsec/deg.
DEC: b = -0.084 arcsec/deg, c = -1.332 arcsec/deg.

RMS residuals: 6.2 arcsec


Feb 27, 2013

This night was dedicated to pointing & tracking tests over a wider area of sky than previously.
The fits are different from before. The rms is 8 arc RA, 12 arcsec DEC. The slopes are:
RA: b = 0.829 arcsec/deg, c = -0.275 arcsec/deg.
DEC: b = 0.051 arcsec/deg, c = -0.853 arcsec/deg.


Mar 25, 2013

This night was also dedicated to pointing & tracking tests over a wider area of sky than previously.
The fits are different from before. The rms is 8 arc RA, 3 arcsec DEC. The slopes are:
RA: b = -0.190 arcsec/deg, c = 0.139 arcsec/deg.
DEC: b = -0.368 arcsec/deg, c = 0.049 arcsec/deg.