The systematics reported previously in heterodyne pointing lead to suspicion that the SCUBA-based pointing model may not be applicable per se to the heterodyne receivers. Since the obvious difference between SCUBA and the heterodyne receivers is the location of their focal stations (Nasmyth -vs- cabin) there arose the possibility that some form of cabin flexure was at play, and that cabin flexure pointing terms might be needed to model heterodyne pointing. This can be checked simply by seeking TPOINT solutions to heterodyne pointing data. Using the current 7 parameters (IE CA IA NPAE AW AN TF) the plots below show the results of fitting pointing data from March 2005 for RxA and RxB, respectively:

There are no remaining obvious systematics - especially none affecting the azimuth residuals (dS) -vs- elevation/zenith distance (centre-left panel in each plot). Fitted RxA/B data have rms's in (dS,dZ) of (1.6",2.6") and (1.5", 3.1"), respectively. Some night-to-night collimation changes probably increase the scatter in the elevation residuals above those that might be seen on any single night, but the azimuth performance seems particularly good, and significantly better than was reported previously. Certainly on the basis of these analyses no additional pointing terms seem needed to resolve the SCUBA-vs-heterodyne differences.