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<H1><A NAME="SECTION00610000000000000000"> </A>
<A NAME="ccd:introduction"> </A>
<BR>
Introduction
</H1>
This chapter describes the design and the philosophy of the CCD package,
its main features, and how to use the tools most efficiently.
<P>
With the installation of new instruments on the La Silla Telescopes in
addition to the availability of CCDs offering large pixel areas and
higher quantum efficiency, the variety of observing modes has grown
and, as an obvious consequence, the amount and the diversity of data
taken have dramatically increased. It is clear that the MIDAS CCD
reduction software should be able to cope with these improvements
and hence requires compatibility with the hardware as it is
offered to the community.
When designing the basic layout of the CCD software the following basic
requirements were kept in mind:
<UL>
<LI>it should be robust;
<LI>it should be user friendly, easy to use;
<LI>it should offer processing possibilities for a large variety
of instruments;
<LI>it should be able to operate both in an automatic mode (to handle
large quantities of data) as well as in single command mode (for
single image analysis);
<LI>it should offer flexible reduction procedures;
<LI>it should be intelligent.
</UL>
How intelligent the system is depends on the capabilities of other
parts in the data acquisition, archiving, and reduction systems. In
this respect the development of the CCD package took place at the
right time: the MIDAS Data Organizer package offers the
possibility to quickly create a MIDAS table containing the science
frames to be reduced and their associated calibration frames. The CCD
package uses this facility that is based on selection criteria,
similar to the ones that are used for the MIDAS table file system.
Also, the ESO Archive project has accomplished that a number
of telescope and instrument specifications, needed to come to a
(partially) automated CCD reduction, can be retrieved from the frame
descriptors.
In order not to re-invent the wheel, existing CCD packages have been
consulted, and, when useful, ideas have been implemented in the MIDAS
CCD software. Its design has largely profited from the IRAF CCDRED
package written by Frank Valdes. Parts of its documentation are used for
this manual. Also, discussions with Peter Draper, the author
of the STARLINK CCDPACK package, are acknowledged.
The document is split into several sections. They describe in detail
the various steps in the CCD reduction, starting from reading in the
science and calibration frames and ending with the final cosmetic fix up
of the final calibrated frames. Some background information about
CCD detectors can be found in the MIDAS Users' Guide, Volume B, Appendix B.
Additional information about the CCD commands can be obtained from their
help descriptions.
The emphasis of the CCD package is on direct imaging. However, since
the first processing steps for spectral data are rather similar to
direct imaging major parts of its functionality can also be used for
processing these data.
<P>
<DIV ALIGN="CENTER">
<B>*** WARNING ***</B>
<BR>
</DIV>
The MIDAS CCDRED context is partly based on the current status of the
ESO Archiving project as well as the Data Organizer Context, in
particular with regard to exposure types and naming of files. Since
both projects may be subject to changes in the future, and because of
user experiences and suggestions for improvements, the CCDRED context
may undergo adjustments accordingly.
<P>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-15</I>
</ADDRESS>
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