![](Fig1.gif)
Figure 1. This figure shows the tilts required to correct
for the translation of the secondary mirror owing to the flexure of
the secondary truss and the flexure of the secondary actuator
supports as a function of telescope elevation angle. The translation
of the secondary mirror with respect to the primary mirror causes
coma in the telescope optics. The tilts shown here are those required
to correct for the coma measured by the Shack-Hartmann sensor.
The squares show the tilts required in the y direction. There is
no measurable variation of y-tilts as a function of telescope
elevation angle. There is a small constant offset of about 5
arcseconds which is the result of errors in the initial collimation.
The circles show a clear variation of x-tilts as a function of
elevation angle. This is the direction of tilt expected from sag in
the telescope truss and secondary actuator supports. The solid line
shows a fit to these data. The lower legend gives the form used for
the fit. The coefficients m1 through m3 must be added to the current
TCC tilt coefficients.