Az, Za model offsets and the horn survey.


    The receivers are positioned using a theodolite survey. The telescope pointing model is then made with the sbn receiver. After the model is made, sources are tracked with sbn (using the new model) and then retracked with the "other" receiver. The pointing offsets are then used to compute the az, za offsets for these "other" receivers. If the receivers had  all been positioned correctly, then the az, za pointing model offsets for all receivers should be the same.

may04 model 15 pointing offsets:

    The receivers were surveyed into position and then resurveyed on 02may04. Pointing model 15 was made after this. The sbn and the lbw receivers were not moved in the x (za) direction because there was no room in the hole in the turret floor.
    The plot shows the az, za pointing offsets (.ps)  (.pdf)  by receiver for model 15.     To include the survey residual errors for za, I used 13.88 Asecs/cm. This conversion factor comes from   45 asecs sky/turret degree. The conversion factor I have of 17.04 asecs/cm for the x direction caused a larger scatter in the green +.

    After correcting for the residual survey error, the rms scatter in the za pointing offsets was 1.7 asecs. This corresponds to about 1 mm rms in linear motion.

processing: x101/optics/hornpos/