Previous: Dark count
Up: Notes to the observer
Next: CCD gain
Previous Page: Dark count
Next Page: CCD gain

Flat fielding

A bright quartz lamp should be used with a dekker size a few steps larger than that used for the object observations, but order overlapping should of course be avoided. It is important to ensure that all orders are as bright as possible. It may be necessary to use different flat field exposures to obtain good frames when observing in a spectral region where the quartz lamp intensity or detector efficiency changes rapidly. Each flat field frame should be constructed by calculating the median of a large number of runs where possible. If you wish to include the errors on the flat field then they should be placed in the flat field variance array. If no variance estimates are provided then the package will assume root N statistics apply. The package can utilise different flat field frames for different orders if required.

Mon Mar 14 16:50:31 GMT 1994