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ECH_FFIELD
Function
Model flat-field derived per-pixel photometric corrections.
- Adapted from the PAMELA routine MAKEBAL.
Summary
Creates a balance factor frame from flat-field frame. This is done
by fitting polynomials to the one-D profiles of the frame in both X and Y- and then dividing these by the frame itself. Negative or zero
pixels and those outside the region specified are set to unity. The
result, when multiplied into a data frame corrects for short-scale
sensitivity variations. Large scale variation can be removed using
either a flux-calibration frame, or if unavailable, the ech_fitblz
option will model the large scale variations.
This version adds the calculation of variances on the balance factors
and also alternatively allows a frame of pre-calculated balance
factors (prebalanced=YES) to be used.
It also allows separate activation of both types of polynomial
fits, interactive fitting, and the calculation of variances.
A typical interactive plot appears below.
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Martin Clayton
mjc@star.ucl.ac.uk
Mon Dec 9 17:09:34 1996