SYNDARK
Name
syndark
Purpose
Create a synthetic CCD dark frame with optional overscan
Description
Adds a base dark image to a bias frame that is created by synbias,
which adds a bias level (overscan level) and simulated read noise to an
arbitrary base image- an optional overscan area contains bias and
read noise only. The sigma is specified for the read noise, which
is normally distributed wih a mean of 0. The output is an
integer array.
Category
CCD data processing
Calling Sequence
syndark,darkbase,etime,gain,biasbase,biaslevel,rdnoise,seed,darkframe
Inputs
darkbase = 2-D input array. This is conceptually a constant, normally
floating point, with each pixel in units of counts/sec.
etime = exposure time in seconds, which is a multiplier for darkbase
gain hypothetical gain (e-/DN) for statistics.
biasbase = 2-D input array. This is conceptually a constant, normally
floating point, with each pixel in units of D/N (counts).
It represent the bias structure introduced by the electronics.
biaslevel integer or float, bias (overscan) level, in units of D/N (counts)
rdnoise integer or float, in electrons/pixel. Sigma for bias is
rdnoise/gain.
seed for random number generator- both input and output.
Optional Input Parameters
Keyword Input Parameters
OVERSCAN - integer, number of columns for the explicit overscan area.
if less than or equal to 0, there is no overscan area generated
and the dimensions of the output array match biasbase.
FITSFN - Fits file for the output dark frame. Exposure time is included
in the header. The default is to generate no file.
CRSNUM - Average number of cosmic ray strikes per ccd area of image.
CRSMAX - maximum D/N for cosmic ray strikes that will be added to the
output. Intensity of each CRS is drawn uniformly over the
range [CRSMIN,CRSMAX].
CRSMIN - minimum D/N for cosmic ray strikes that will be added to the
output.
Keyword Output Parameters
CRSOUT - Output, number of cosmic rays added to the image.
Outputs
darkframe - 2-D int array that is the synthetic dark image. It's dimensioned
n x (m + o) where n, m are the dimensions of darkbase and
o is the number of overscan columns created. The overscan
area of the dark is darkframe[n:n+o-1, *]. Pixels are
in units of D/N counts.
Pixel values are calculated in floating point and rounded
and rounded to nearest integer. They are truncated at 32767.
Common Blocks
Common Blocks
Side Effects
Restrictions
Only handles single images- the darkbase and biasbase must be identically
dimensioned.
Procedure
Modification History
2006 June 28, Written by Peter L. Collins, Lowell Observatory
2006/07/10 PLC, reorder arguments for consistency
2006/7/12 PLC, CRS keywords- other documentation and argument cleanups.
2006/07/13 PLC, add keyword CRSOUT.
2006/07/14, MWB, final cleanup and addition to library.