Central bearing measurement

Summary
As seen last time ( 981102 ), the empirical correction is still overcompensating by about 1".

N2071IR was tracked, using the SCUBA map16 method, and with the empirical corrections enabled, from (az,el) = (251/42) at 05:29 HST to (261/24) at 06:46 :

The del residuals show no baseline trend and have an rms of 0.3", equal to the seeing during this period. Taking account of the mild baseline trend in daz, the azimuth residuals show about a -1" deficit at about azimuth 255 and a +1" error at about azimuth 258. The center of the event occurs approximately at (az,el) = (256.5,33.8), with the location in azimuth being as expected (256.6) to within 0.1 degrees. This implies that the current empirical correction, with a (semi-)amplitude at the horizon of 7.1", is overcompensating by a little over 1". The current measurement implies a (full, peak-to-peak) amplitude at the horizon of 11.8".

NB : There is a track joint at azimuth 252 (wheel 1 at joint 1/2), but any difference between the track profile today and the current track model (see the report of 981107 on the resurgence of apparent inclinometry changes) seems to be having little or no effect on pointing on a scale more than 1".

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