Package configuration

Package configuration is performed using the CCDSETUP program. This sets the values of a sequence of global parameters, that are used by the other CCDPACK programs. Starting with this routine serves as a useful reminder of what values etc. will be required to perform the reduction. Note, however, that none of the parameters are compulsory (indeed CCDSETUP itself is not compulsory) and may be returned as `!' (this is the null-value symbol). CCDSETUP asks for the following values (together with some others which are best accepted until more experience with the package is gained):

• The ADC factor which converts the ADUs of the input data frames into detected electrons (this also used to generate errors).
• The bias strip positions (used for offsetting the master bias frame or for bias estimation).
• The readout direction (defines bias strip positions and the bias interpolation direction).
• The typical readout-noise (also used to generate errors).
• The useful CCD area.

The routine also initialises the CCDPACK logging system (see later).

Which of this information you'll have to supply depends on whether or not your data has the correct information stored with it. CCDPACK can ``import'' FITS headers and use these to supply the necessary information.

A typical CCD geometry is shown in Figure ; note how the bias strips and useful CCD areas are defined. The coordinate values for these regions are always defined in pixel indices (i.e. row or column numbers, usually starting at 1,1 for the lower left-hand corner of the data array).

A typical set up command is:

% ccdsetup adc=1.5 bounds='[2,10,400,416]' rnoise=10 extent='[11,399,1,576]'

In this example certain required characters (the [ ]) are also special to the C shell so must be protected.

CCDSETUP also allows you to define which parts of the CCD are corrupt or unreliable (due to hot spots, bad columns etc.); see the section on data-masks, if you need to do this.

Figure: Typical CCD geometries. In the figure on the left the readout direction is `Y', the bias strips are located with bounds I,J,K,L and the useful CCD area is M,J+1,N,K-1 (ish, you should probably use more than $\pm 1$). In the figure on the right the readout direction is `X', the bias strips are located with bounds I,J,K,L and the useful CCD area is N,J+1,K-1,M-1 (N.B. some observatories recommend that you only use the left-hand strip, if you use the right-hand one too, check that it isn't contaminated by residual charge).