.help lickbase 1995July lick.lickbase
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NAME
lickbase -- Fit and subtract an average column bias to Lick images
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USAGE
.nf
lickbase input output
.fi
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PARAMETERS
.ls input
Images to be bias subtracted.  The images may not contain image sections.
.le
.ls output
Output bias subtracted images.  An output image may be the same as its
matching input image.
.le
.ls rdnoise
If this value is >= 0., a RDNOISE card will be inserted with the value.
This applies to readouts which are not denoted 'Fast' by the CLKSPEED card.
.le
.ls rdnoisef
If this value is >= 0., a RDNOISE card will be inserted with the value.
This applies to readouts which are denoted 'Fast' by the CLKSPEED card.
.le
.ls gain
If this value is > 0., a GAIN card will be inserted with the value.
This applies to readouts which are not denoted 'Fast' by the CLKSPEED card.
.le
.ls gainf
If this value is > 0., a GAIN card will be inserted with the value.
This applies to readouts which are denoted 'Fast' by the CLKSPEED card.
.le
.ls gainb
If this value is > 0., a GAIN card will be inserted with the value.
This applies to readouts which are not denoted 'Fast' by the CLKSPEED card,
and which are binned in either dimension.
.le
.ls gainbf
If this value is > 0., a GAIN card will be inserted with the value.
This applies to readouts which are denoted 'Fast' by the CLKSPEED card,
and which are binned in either dimension.
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.ls pixtrim
An image section which will be inserted as an IRAF TRIMSEC card.
This image section is expressed in a 1-based system (as in all IRAF and
WCS usage), but in the coordinate system of the original, unbinned
pixels on the silicon of the CCD.  This permits a trim section to be
specified and used on images which had different binning.
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.ls dispaxis
If this value is > 0, a DISPAXIS card will be inserted with the value.
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.ls observat
If this value is not null, an OBSERVAT card will be inserted with the value.
.le
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DESCRIPTION

This task performs the baseline subtraction on images obtained
with the Lick Observatory data acquisition system.
After this tasks Lick images are prepared for further processing with IRAF.

For each input image in the input image list the last column is assumed to
be a baseline column as would be produced by the Lick Data Acquisition Systems
on Mt. Hamilton.  The appropriate manipulations of the image are made,
and then the \fBcolbias\fR task is called to perform the bias fitting.

It is required that the IRAF parameters for the \fBcolbias\fR task have
already been set before running \fBlickbase\fR.  Specifically, the user
will wish to ensure that the "function", "order", "*_reject",
and especially the "interactive" parameters are correctly set.

As the image is output, the OVERSCAN card and several other cards which are
useful for the \fBccdproc\fR task are inserted with suitable values.
Images which already contain an OVERSCAN card will be flagged and
not modified by this task.  Thus, it should be safe to run this task
twice over the same images without causing any harm.
The image is not trimmed, but the TRIMSEC card is inserted so that
\fBccdproc\fR will be instructed to trim off the last column.


The parameters rdnoise, gain, dispaxis, and observat are for convenience.
The Lick data-taking system does not insert these cards, but several
IRAF tasks make use of them.

Note carefully that, as far as \fBccdproc\fR
is concerned, a binned detector is a different detector than the same
detector with unit binning.  The value of the RDNOISE card should be
different for a binned detector.  The value of GAIN can also vary
depending on fast/slow readout modes and over time.  Furthermore,
when any kind of binning is requested on a Lick CCD, the gain of
the amplifier is automatically reduced by a factor of 4.

If rdnoise is specified, it should be given in electrons (i.e., photons),
NOT in DN.  If gain is specified, it should be given as the number of
electrons (photons) per DN.
See, e.g., \fBimcombine\fR, \fBapphot.datapars\fR, and \fBapall\fR for
discussion of the use of RDNOISE and GAIN.

DISPAXIS is used by many of the spectral extraction tasks.  OBSERVAT is
used to set the position of your telescope for airmass, position
angle, and other such calculations (see \fBobservatory\fR).

N.B.:  \fBlickbase\fR places temporary files in the directory specified by
the IRAF cl variable "tmp".  It is advised that you "reset tmp =
/a/big/local/disk" in your loginuser.cl file.
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SEE ALSO
colbias
ccdproc
ccdgeometry
lickast
.endhelp