SUMMARY
Recently problems have been reported with the pointing. The last 3 nights of data allow some analysis, but there does not appear to be any immediate solution available via the parameters of the pointing model.

The three datasets are summarized below :

   Datasets     No. of points   uaz   +-     uel   +-

  PT990524_16         21       -0.2  2.3    -1.4  2.3
  PT990525_18         15        1.8  2.7     0.8  1.9
  PT990526_15         21        1.1  2.3     0.9  1.8

- and added together they appear in the following figure :

The most noticeable feature is the strong variation of daz with azimuth in the azimuth range 90-180. Unfortunately it is not amenable to 'flattening' by changing any of the 7 parameters of the telecope model - allowing all 7 parameters to vary in order to minimize the residuals produces the 'fit' below :

The cause and solution of this systematic problem are being sought, but in the meantime it is clearly important that its effects be mitigated by local pointing.

990530
Another dataset was acquired the next day :

   Datasets     No. of points   uaz   +-     uel   +-

  PT990524_16         21       -0.2  2.3    -1.4  2.3
  PT990525_18         15        1.8  2.7     0.8  1.9
  PT990526_15         21        1.1  2.3     0.9  1.8
  PT990527            18        8.3  2.1     5.8  1.5

even if the coverage of the critical azimuth range is incomplete.