There are two programmes for the basic photometric reduction:
fotmon for when the data was obtained in the sky chopping mode,
and fotmo for data obtained in the non--chopping or single channel
mode. For the latter, the sky background measurements must be
indicated by a measurement code 3, as first digit on the line
containing the star number. If more than one sky measurement has been
taken the programme makes a linear interpolation with time, assuming
that the star number has not changed.
The raw photometric data contained in the output file from polred
as part of the polarisation measures, can be extracted and written in a
more compact form by the programme fotli, which also puts the data
into the same format as the output files from fotmon and
fotmo. The magnitudes are the average of the 8 sub--integrations
done in polarisation mode; higher time resolution can be obtained by
running the programme fastfot, which computes the magnitudes from
each individual sub--integration.
For further reduction, a file (e.g. staf.sta) containing the following
information must be made:
1234 6789.1234 0.123456 12.45 16.72 0.0038 0 0 0 0 0 67321 0. 0. 11.68 24.54 0. 9.432 .249 .362 .453 .395 etc.
where the columns give the star number, epoch of minimum light (Julian
day number), period (days), 
, 
(both in decimal form),
heliocentric correction (days), V, U--B, B--V, V--R, and V--I (in
magnitudes). The magnitudes and colours are given only for standard or
comparison stars and should be entered as zeroes for programme stars.
There are two programmes for differential photometry reduction:
fotlim, giving UBVRI magnitudes, and fotlin which gives V,
U--B, B--V, V--R, and V--I. Both programmes compute the extinction and
transformation to a standard system with coefficients in the
programme. This gives satisfactory results for differential photometry
where by the object and comparison star are not too far apart both on
the sky, and in spectral type. The zero point correction can be
interpolated between each comparison star observation with the
programme fotout which uses the output files from fotlim and
fotlin as input, and lists the final results for the science star
observations in its output file.