Under construction

1. There is a +4" change in elevation pointing across transit. The effect occurs mainly in the azimuth region within 5 degrees of the meridian. See the plot
2. The effect seems independent of elevation at transit (declination), and is essentially the same in the north and south.
3. The pointing model does not expect such a 'misalignment' in the antenna, but compensates for it as best it can - by assigning an additional amount of tilt to parameter #2, the E-W tilt of the azimuth axis.
4. Uniform 'allsky' pointing will then show a pattern of residuals with at most 2" deviations.
5. Non-uniform allsky pointing and subsequent model fitting will leave other patterns of residuals.
6. Specifc pointing tests, on targets or pairs of targets with specific (az,el) coordinates, will show differences in pointing peculiar to the precise residual pattern left following the model fitting. (see the various experiments carried out so far .) Fitting all of the observed results into this picture has not yet occurred, but the sizes of the pointing changes seen in any one experiment are consistent with the small residuals expected from this picture.
7. Correcting the problem in the telescope software should be possible, either as a lookup table or as some functional form (tricky).
8. Tracking through transit should be avoided until this corrective term is installed into the pointing model, or corrected manually, and regularly, if you feel confident.