FIXERR N1 N2 NSECT CMAX SET -- Fixes error bars of low count number data
Parameters
N1 -- First spectrum to fix
N2 -- Last spectrum to fix
NSECT -- Number of sections to split spectra into
CMAX -- Error only corrected if number of counts in a pixel
is below this threshold.
SET -- Set mask to avoid bad regions of spectra
With very small numbers of counts it can be difficult to assign good
error bars. The obvious procedure of SQRT(Number of counts) is a bad
idea since if there are no counts, an error bar of zero is assigned.
If there are similar spectra taken at the same time (or better still the
same phase), they can give some idea of the mean count rate and
hence help in setting an error bar. This routine was designed with HST
data in mind. The counts are collapsed in the spectral (--> mean spectrum)
and time directions (--> light curve) and then predicted counts are derived
by mutiplying the two for each spectrum. Bad spectral regions can be removed
from the light curve by setting a mask over them at the start. The light
curve is formed separately in NSECT sections and linearly interpolated from
one to the next to allow for possible colour variations.
This command belongs to the class: fudging