SYNBIAS

Name

synbias

Purpose

Create a synthetic CCD bias frame with optional overscan.

Description

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 through the read noise and gain,
and is normally distributed wih a mean of 0. The output is an
integer array.

Calling Sequence

synbias,biasbase,biaslevel,gain,rdnoise,seed,biasframe

Inputs

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]
gain hypothetical gain [e-/DN] for statistics.
rdnoise integer or float, [e-]. Sigma for bias is rdnoise/gain
seed for random number generator.

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. 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

biasframe - 2-D array that is the synthetic bias image. It is dimensioned
n x (m + o) where n, m are the dimensions of biasbase and
o is the number of overscan columns created. The overscan
area of the bias is biasframe[0:n-1, *] This is an array
of ints and the units are D/N [counts]. Pixel values are
calculated in floating point and rounded to nearest integer.

Common Blocks

Side Effects

Restrictions

Procedure

Modification History

2006 June 28, Written by Peter L. Collins, Lowell Observatory
2006/7/10, PLC add COSMIC keyword
2006/7/12, PLC CRS keywords- other documentation and argument cleanups.
2006/07/13, PLC, add keywords CRSOUT and STARSOUT.
2006/07/14, MWB, final cleanup and addition to library.