Telescope model updated

Reports of poor pointing started appearing on Dec 26, and a display of that night's pointing data showed a strong trend between the azimuth residual and elevation - indicative of a 12" change in parameter #3 - the non-orthogonality of the major axes. A similar trend was seen the following night. These data were taken with RxB3, which had its own problems at that time, and so I was reluctant to implement a change immediately. However, problems continue to be reported and in retrospect similar trends are visible in SCUBA data taken after the change of temp_slope on 971222 , and up until the point that SCUBA was warm ed up (971226). These data are shown below :

Dropping the omc1 point (that with the most negatibve value of daz ), and running the data through the FIT9 program shows the need to change the telecope parameters by the following :

       parameter #   1     2     3      4      5     6     7
                   1.2  -0.2   6.7     4.3   -0.4  -0.2   2.9

Comparing these with earlier changes :

       (971218)   -0.7  -0.1   1.8     6.4    6.9   1.2  -2.5 
       (971217)    0.2   0.1  -7.3   -14.9  -12.7   0.0   0.1  

reveals that all parameters have essentially returned to their values prior to 971217 (#5 has changed as a result of the change to temp_slope ).

The new model gives the following pointing residuals :

The pointing model has been updated, although I note that RxA2 data from the last 2 nights do not support this (or any) model change. Further updates seem inevitable.