iraf.net

I am using ccdproc (noao.imred.ccdred), and I have a question abut the parameter: readcor. In the help page it says "Convert zero level images to readout correction images?.... etc" but I don't really know what this means... (it obviosly should be something different than zerocor), but I don't get it.

Does my question make sense? Do you want me to explain it more?

Readcor is used in cases where the zero level bias is dependent on the readout. In this case a 2-D zero image it will be averaged across the readout axis specified by the 'readaxis' parameter. Whether you need this depends on the nature of the detector, or whether you observe in "longscan" mode (i.e. a continuous readout to produce an arbitrarily long strip).Unless you know the detector requires it, turn it off.-Mike

Thanks , that makes sense.
What about the scancor? does it also depend on the detector? what does it do?
"looking in the help page it say: convert zero level , dark count and flat field images to scan mode flat field images?" why would anyone do that?

Is this something that depends on the detector?

'Scancor' refers to an observing mode more than the detector specifically. In most cases the CCD is exposed for some time while the telescope tracks the object, in "scan mode" the CCD is clocked to read out continuously to produce a "strip" that may be longer than the physical detector. This might be used to e.g. observe a fast-moving minor planet or a transit observation for some reason.

So it's something technical that the one who takes the data using the telescope should worry about, and once data is taken it's a default (given parameter), right?

Only turn it on if you know the data were taken using this kind of scanning mode. The default is 'off' because most data are taken the "normal" way.