In principle, if the track is sufficiently well measured, actual variations in the height of the track should not be a problem. In practice however, we have had difficulty characterizing the track well enough, and so large errors in the pointing do occur at certain azimuths. These can be especially invidious if they occur while tracking a source, rather than while actually doing pointing measurements.
In addition to this difficulties this poses for observing, however, there have been worries about the mechanical integrity of the track. There are concerns that the track may deteriorate with time, unless remedial action is taken. In addition, there is a possibility that large discontinuities at track joints might cause damage to the azimuth rollers.
Accordingly, we propose to install azimuth track ``leveling brackets''. These should both stabilize the track from further deterioration, and improve the absolute tracking stability of the telescope.
Obviously, these brackets cannot be installed until we are confident that we are capable of characterizing the track again immediately afterwards.