% @(#)illcorccd.hlq 17.1.1.1 (ESO-IPG) 01/25/02 17:48:53 %++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %.COPYRIGHT (c) 1993 European Southern Observatory %.IDENT illcorccd.hlq %.AUTHOR RHW, IPG/ESO %.KEYWORDS MIDAS, ccd package, ILLCOR/CCD %.PURPOSE On-line help file for the command: ILLCOR/CCD %.VERSION 930827 RHW Documentation created %--------------------------------------------------------------------- \se SECTION./CCD \es\co ILLCOR/CCD 25-Mar-1993 RHW \oc\su ILLCOR/CCD [in_spec] [out_frm] [xboxmn,xboxmx] [yboxmn,yboxmx] [clip] [lowsig,higsig] Make flat field illumination correction frame(s) \us\pu Purpose: Make flat field illumination correction frame(s) \up\sy Syntax: ILLCOR/CCD [in_spec] [out_frm] [xboxmn,xboxmx] [yboxmn,yboxmx] [clip] [lowsig,higsig] \ys\pa in_spec = single flat frame or MIDAS CCD association table (with the extension .tbl) containing the names of the flat frame(s) in the column :FF. Default input is taken from the keyword CCD_IN. \ap\pa out_frm = name of the output illumination frame. Default output is the name of the input table with extension "_ill". Only used in case of single frame input for the first parameter. In case the input is a MIDAS table the name(s) of the output frame(s) will have the same name as the sky frame field expanded with '_ill' (see below). \ap\pa xboxmn,xboxmx = minimum and maximum smoothing box size along the x axes. The minimum box size is used at the edges and grows to the maximum size in the middle of the image. This allows the smoothed image to better represent gradients at the edge of the image. If a size is less then 1 it is interpreted as a fraction of the image size. If a size is greater than or equal to 1 then it is the box size in pixels. A size greater than the size of image selects a box equal to the size of the image. Default values are taken from the keyword IL_XBOX. \ap\pa yboxmn,yboxmx = see above. Default values are taken from IL_YBOX. \ap\pa clip = Clean the input frame(s) of objects? If yes then a clipping algorithm is used to detect and exclude objects from the smoothing. Default taken from IL_CLIP. \ap\pa lowsig,higgsig = sigma clipping thresholds above and below the smoothed illumination. Default values are taken from the keyword IL_SIGMA. The keyword is only read in case clip=yes. \ap\no Note: The command operates very similar to the command REDUCE/CCD, which the exception that the command not check for the exposure type of the input frame. In case the input is an association table the command will check for the existence of the flat frames. Flat frames that do not exit will be created first, provided the association table contain the flat column. Other relevant calibration frames for processing the flat frames, will be taken from the corresponding calibration columns belonging to the same science frame. Output illumination frame(s) will have the same name as the original flat frame except for the extension `_ill'. In the case of single frame input and all calibration frames input will be taken from the SC_ keywords and must exist.\\ The input flats are automatically processed up through dark current calibration before computing the illumination pattern. The illumination correction, the inverse of the illumination pattern, is applied by the CCD package to remove the illumination pattern introduced by the flat field. The combination of the flat field calibration and the illumination correction based on the flat field is equivalent to removing the illumination from the flat field (see ILLFLAT/CCD). This two step calibration is generally used when the observations have been previously flat field calibrated. This task is closely related to SKYCOR/CCD which determines the illumination correction from a blank sky frame; this is preferable to using the illumination from the flat field as it corrects for the residual illumination error.\\ The illumination frame is produced by heavily smoothing the calibrated flats frames using a moving "boxcar" average. The effects of objects in the frames may be minimized by using a sigma clipping algorithm to detect and exclude the objects from the average. The output illumination frame can used by REDUCE/CCD to remove the illumination pattern in the science frames.\\ The IM_SEC keyword may be used to assign a region of interest for which the correction has to be done.\\ For more information see the CCD chapter in Volume B of the User's manual. \on\see See also: SET/CCD, SHOW/CCD, HELP/CCD, REDUCE/CCD, SKYFLAT/CCD \ees\exs Examples: \ex ILLCOR/CCD ccd_asstbl.tbl Reduce all flat frames in the flat field column in the ccd table ccd_asstbl.tbl. Master calibration frames will be obtained from the same table. Do the calibration according to the keyword settings. After the calibrations are done create the illumination frames, using the `IL_' keyword settings. Calibration frames will be taken from the table redtbl.tbl \xe\ex ILLCOR/CCD m100rraw m100rraw_il Start the ccd reduction sequence for the frame m100rraw. This input frame should be present. The output frame will be m100rraw_il. In case only dark correction is to be applied the name of this calibration frame will be obtained from the keyword SC_DKFRM. \xe\sxe