SUMMARY
The correction for the elevation pointing problems occurring across transit seems to work OK.

To combat the elevation pointing problems associated with the reversal of direction in elevation - the 'transit' problem - a new version of tel_empirical.dat was installed on 16 May 2000. It was tested tonight for the first time by tracking 3c279 from (az,el) = (168,64) at HST 20:52 to (191,64) at 21:33. Seeing was 0.9" typically. A SCUVAX clock error of -6^m22^s was discovered that permeates the data file headers. After correction of the recorded LSTs, the data are shown below :

The data are somewhat ragged but show no sign of the 4" s-shaped change across transit seen in the pre-correction data . The apparent systematic trends in del are matched (mirrored in the period prior to transit) by those in daz, and they are both therefore probably artifacts of the poor conditions. To this extent the correction seems to perform satisfactorily, although further data would be desirable. The impact upon allsky pointing of the new version of tel_empirical and the associated changes made to parameter #2 of the pointing model have yet to be assessed.