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. CATEGORY: CCD data processing 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.