The on-chip guiding system has been tested successfully on sky during engineering runs of WIRCam in April and May 2005. Figure 4 shows the spatial frequency spectrum of the star guiding movement at full speed (50 Hz) open loop, closed loop and closed loop with TCS guiding. Low frequency movement is suppressed by about 30 dB. The crossover is between 6-8 Hz, which corresponds to the closed-loop tuning model used to set the PID parameters. Guide stars to the 14th magnitude were tested.
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