NAME: skyim PURPOSE: (one line only) Calculate a smooth sky image from 2-d polynomial fit coefficients DESCRIPTION: CATEGORY: CCD data processing CALLING SEQUENCE: skyim,dimen,coeff,skyimage INPUTS: dimen - Size of array to compute [nx,ny] coeff - Coefficients of fit xorder - order of fit to X direction (default=0, constant) yorder - order of fit to Y direction (default=0, constant) Length of coeff must be (xorder+1)*(yorder+1) OPTIONAL INPUT PARAMETERS: KEYWORD INPUT PARAMETERS: OUTPUTS: skyimage - Smooth image of sky in image. KEYWORD OUTPUT PARAMETERS: COMMON BLOCKS: SIDE EFFECTS: RESTRICTIONS: PROCEDURE: MODIFICATION HISTORY: Written by Marc W. Buie, Lowell Observatory, 2004/07/06 2010/11/30, MWB, fixed problem with constant sky value option