Skydip Routine - DIP

The skydip routine has no user-adjustable parameters. It is initiated by typing the keyword DIP while the telescope is under computer control. It is not necessary to switch from spectral line to continuum modes. The sequence of events is as follows:

1. telescope moves to 1.5 airmasses, measures hot load, sky, and blanked voltages, and then computes a CAL value.
2. telescope then moves to 2.5, 3.5, 3.5, 2.5, and 1.5 airmasses, repeating the above calculations.
3. finally, two determinations of the zenith opacity TAUZ are made, and the average saved for use in calibrating data, as well as the computed atmospheric temperature, TATM .

If the user views screen 11 while the dip is in progress, the various measured and computed quantities will be updated as the dip proceeds. The screen retains the data from the last DIP until the next one begins. The newly computed average opacity, TAUZ , is also displayed on screen 1.

The value for TATM can also be set by the user. After a DIP , both the computed value of TATM and the applied value of TATM are set to the result from the DIP program. The user can then examine those values on screen 11, and, if unhappy with the computed value of TATM , can override it by typing TATM (value in Kelvin). The new value will apply until the next dip is done.