Dataset      N        mean uaz +-     mean uel +-
 
     pt010109     47          -3.0  2.5     -0.3  1.6

The data are plotted in their many ways here. Seeing was 1.0" for much of the shift, dropping to 0.6" by the end. The data show rather little in the way of systematic trends : in particular, there is no evidence for any deficiency in the s-correction : which would appear as a step in the del-vs-azimuth plot at az=180. The one exception is perhaps in the way daz varies as a function of azimuth :

(Click on image for better view)

After allowing all 7 of the TPOINT pointing model parameters to float to new, optimal values these data show a suppressed, but resistant, systematic pattern :

Vector RMS residuals (ie the quadratic sum of the residuals in azimuth and elevation) are expected to be 2.5" with this new model. If equally allocated, this would correspond to errors of 1.7" in each coordinate. This is an improvement on the last reported model change and essentially as good as we have seen in the past.

The new model was installed at 15:10 HST on Wednesday 10 January, 2001.

This version of the above plot contains a speculation on the pattern of the residuals in the daz-vs-azimuth plane : Is there a likely source for such a pattern ?