Tracking of Uranus with RxB and the fives method was performed for about 1.75 hours between HST 00:25 and 02:10. Uranus moved from (az,el) = (125,42) to (157,58); the empirical correction was disabled throughout. Pointing residuals are displayed below:

The race defect reveals itself as +ve & -ve excursions in the azimuth residuals. The green line is the current empirical correction (of amplitude 6" at the horizon) and assumes perfect pointing/tracking otherwise.

The defect amplitude (peak-to-peak) at (az,el)=(141,53) is estimated as 4.0", giving an amplitude at the horizon of 6.6" cf approx 7.0" 6.1" and 5.0" 3.3" previously. The 'trend' seen last time is broken, and the current amplitude seems valid.

The rms of the elevation tracking errors during this period is 0.6".