Page Comparison

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The first line sets the Position Angle (PA) of how you want the instrument's slit pointed at your target on the sky.  The PA goes clockwise from the North where  N=0, E=90, S=180, W=270 degrees.  The default rotation of the instrument is such that the the slit is oriented East to West, so normally the PA = 90 degrees.  WARNING: You should only rotate the instrument +/- 90 deg. from the default position to avoid entangling wires and hoses, so please try to limit your PA to 0-180 deg.  When rotating IGRINS, you will use the encoder on the instrument rotator.  See the Rotation PA -> Encoder table for IGRINS to convert PA to the number on the encoder.  The PA you set will be reflected in how the sky is imaged in the FOV of the slit view camera, as shown below: