HET LRS2 Position Angle Calculator

This program enables a PI to determine the angle on the sky of the LRS2 IFU for a given DEC and track. The east and west tracks may have different position angles. During a trajectory the tracker makes some rho rotation in order to keep the orientation fixed on sky. When we refer to the parallactic angle we really mean the parallactic angle at center of track.

The current limits for the rho rotation are -21 and +21 relative to the parallactic angle for center of track, but almost all of this is needed to keep the constant angle on the sky during a trajectory in the North.

We define position angle as positive measured from north through east.
The parallactic angle is perpendicular to the long axis of the IFU. It may help to consult this page for additional information: https://hydra.as.utexas.edu/?a=help&h=105

Enter the Dec below (results for the parallactic slit angle will also be returned).

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