The essential steps are: (1) division of the data by the integration time (stored in descriptor O_TIME), (2) subtraction of the sky and the offset (using a sky measurement, if available, or a dark measurement), (3) calibration (division by calibration file) and (4) Fourier transformation. As is described in Appendix A of the PISCO Operating Manual, the last step, a simple Fourier transform using the MIDAS command FFT/POWER, is the core of the reduction of PISCO data.

The procedure is designed to handle an entire set of data by operating on an input catalog and producing a single output table in which each row holds the results for one data frame in the input catalog. There are no free parameters except for a

The program attempts an error estimate from the noise level in the Fourier-transform. The polarisation angles still have an arbitrary zeropoint and need to be transformed to a standard system by means of observations of standard stars. Apart from the comparison with calibration data, the results of REDUCE/PISCO should be final.

The output table is a standard MIDAS table so that all applicable table commands can be used to further process the results. The columns of this table are shown in Table E.1.

=01 =11 =1992