Footnotes

Usually because another correction may also be necessary - the removal of fringing see appendix

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... all'²

This section does not apply to XREDUCE or IRAF.

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... performed ³

This section does not apply to IRAF/CL users

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... corrections ⁴

An additional effect of interest, which cannot be fully corrected, is the colour sensitivity of the CCD pixels. Most pixels on a typical CCD frame are exposed to the night sky which has a specific colour, this, however, may not be the same colour as the object itself, so the best case response is that the object and night sky colours mix to produce a response not typical to the night sky dominated parts of the frame, if the object is much brighter than the sky then its colour will dominate and ideally the flatfield should be produced with a source mimicking this colour response.

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