.help spotlist May88 imred.dtoi
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NAME
spotlist -- calculate densities of calibration spots 
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USAGE
spotlist spots fogs database
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PARAMETERS
.ls spots
List of image files containing the calibration data.
.le
.ls fogs
List of image files containing fog spots.
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.ls database
Name for output database.
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.ls scale = 0.00151			# (4.65 / 3071.)
The scale factor to convert values in the image files to densities, such
that scale = density / input_value.
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.ls maxad = 3071
The maximum A/D value, that is, the input value corresponding to a
saturated pixel.
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.ls option= "mean"
Option for calculating densities can be either "mean" or "median".
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.ls sigma = 3.0
Rejection criteria for iteratively calculating mean density.
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DESCRIPTION
Task \fIspotlist\fR reads calibration spot images and calculates their
density and standard deviation.  Three records are entered in the
database: density, standard deviation and number of unrejected pixels.
Each record contains as many entries as calibration spots.

All input values are multiplied by the \fBscale\fR parameter to convert
them to densities.  The value of \fBscale\fR is not critical to the 
reductions, it is provided so that \fIspotlist\fR output can be in the 
familiar units of density.  The default value of \fBscale\fR is correct
for NOAO PDS data written to a PDS format tape.  If a FITS format tape was 
written, \fBscale\fR = 0.0001893.  These values are appropriate for the PDS 
with its new 15-bit logarithmic A to D converter.  The value of \fBscale\fR
used is also entered in the database.

Parameter \fBmaxad\fR is the integer input value that represents a
saturated pixel.  This value is used by \fIspotlist\fR to accurately
calculate the density of a saturated pixel, which is then entered in the
database.  This value of "maxden" will later be used by task \fIhdfit\fR
to normalize the independent variable vector, and by task \fIhdtoi\fR to
scale the intensity range precisely to a user specified value.

A fog level is calculated from image \fBfogs\fR, and entered into
the database file.  If more than one image is given for \fBfogs\fR, 
a single fog value is calculated from all fog pixels.  The fog level
is calculated but not subtracted in this procedure.  The fog images to be 
averaged should be the same size.  An entry for the fog level is made
in the database.

The \fBspots\fR files are assumed to be ordered such that they are either
monotonically increasing or decreasing in density, with no omitted spots
between the first and last measured.  The calculated density can be
calculated two ways; the algorithm used is selected by the \fBoption\fR
parameter.  The density is either the mean spot value after pixels more
than the specified number of sigma from the mean value have been rejected,
or the median value of all the spot pixels.  
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EXAMPLES
Calculate mean densities of calibration spots which had previously been
read in from a FITS format tape.  The database "db1" will be created.

.nf
	cl> spotlist spots* fogspot db1 scale=1.893e-4
.fi
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SEE ALSO
dematch, hdfit, hdtoi
.endhelp