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46.6 Flatfield Anomalies

The photometric accuracy of the data is often limited by the quality of the flatfield used to calibrate the data (see "Determining the "Best" Reference Files" on page 45-14 as well as the WWW Reference File and Closure Flat Memos). Details of the flatfields and delta flats available for calibration were discussed in "Determining the "Best" Reference Files" on page 45-14. In this section, we summarize residual features that may remain; we recommend experimenting with different flatfields to determine which are best for the data (see "Improving the Flatfield Correction" on page 46-15).


Note that the neutral density filter effects have not been removed from the SV and the non-SV epoch flatfields; to avoid the problem, use a flatfield close in wavelength that was not generated with the F122M filter or use a -closure or a high fidelity flat2. For further suggestions on improving the flatfields, see "Data Accuracies and Problem Solving" on page 46-13 (see also OV/SV Report, Faber et al., 1992, Chapter 6, and Closure Flatfield Memo on WWW).



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1 WF/PC-1 ISR 92-4.

2 Note that the use of a different flat will affect the photometric calibration.

stevens@stsci.edu
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