% @(#)combinccd.hlq 17.1.1.1 (ESO-SDAG) 01/25/02 17:48:53 %++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %.COPYRIGHT (c) 1993 European Southern Observatory %.IDENT combineccd.hlq %.AUTHOR RHW, IPG/ESO %.KEYWORDS MIDAS, ccd package, COMBINE/CCD %.PURPOSE On-line help file for the command: COMBINE/CCD %.VERSION 930407 RHW created %.VERSION 930517 RHW documentation improved %.VERSION 931101 RHW Released %.VERSION 950113 RHW Changes according to the DO output format %.VERSION 980309 SW Add new method: mmedian = mean-median %--------------------------------------------------------------------- \se SECTION./CCD \es\co COMBINE/CCD 1-Nov-1993 RHW \oc\su COMBINE/CCD exp [in_spec] [out_fram] Combined a number of CCD frames of the same exposure type \us\pu Purpose: Combined a number of CCD frames of the same exposure type \up\sy Syntax: COMBINE/CCD exp [in_spec] [out_fram] \ys\pa exp = exposure code of the frames to be combined. Options area:\\ BS for BIAS frames;\\ DK for DARK frames;\\ FF for FLAT field frames;\\ SK for SKY frames;\\ OT for OTHER frames.\\ The parameter `exp' determines which keyword setting will be used for the combining (see below). \ap\pa in_spec = a) name of a MIDAS table (with the extension `.tbl'), or// b) name of a MIDAS catalogue, or c) string of input single calibration frame, separated by comma's. By default the input is taken from the keyword CCD_IN. \ap\pa out_fram= resulting combined output frame. No default output. \ap\no Note: In case a MIDAS table is used the command expects the name of the output master calibration frames in the column which name should be available from the keyword `exp'_COL. The name of this output master calibration frame should conform to the Data Organizer/CCD naming convention. Obviously, the individual calibration frames must available.\\ The parameters needed for the combining are read from the CCD keyword structure. This keyword setting can be consulted by the command SHOW/CCD `exp_typ', where `exp' can be BS, DK, FF, or SK. The listing shows these keywords, their options and meaning:\\ CCD_IN \ \ \ input spec - input table or catalogue\\ `exp'_SIG\ \ \ yes/no - create sigma and pixel count image?\\ `exp'_TYP\ \ \ all/exp. type - exposure time descriptors allowed\\ `exp'_MET\ \ \ method - method of combining (see below)\\ `exp'_RAN\ \ \ value1,value2 - range of pixel values allowed \\ `exp'_DEL\ \ \ yes/no - delete input frames afterwards?\\ `exp'_EXP\ \ \ yes/no - scale by exposure time?\\ `exp'_STA\ \ \ mean/median/mode - statistics for scaling or offset\\ `exp'_SCA\ \ \ yes/no - scaling required?\\ `exp'_OFF\ \ \ yes/no - offset correction required?\\ `exp'_WEI\ \ \ yes/no - use a weighted average?\\ `exp'_SEC\ \ \ area - area for computing the statistics\\ `exp'_CLP\ \ \ value1,value2 - low/high sigma clipping factor\\ `exp'_BLA\ \ \ value - blank value for rejections\\ The combining will be done according to the method contained in the keyword `exp'_MET. Currently, the following methods are supported:\\ sum - simple sum of all input input images;\\ ave(rage) - input images are combined by averaging;\\ median - input images are combined by medianing each pixel;\\ mmedian - same as median but take the mean in a given interval;\\ min(reject) - reject the minimum value from the average;\\ max(reject) - reject the maximum value from the average;\\ minmax(reject) - reject the minimum and maximum from the average;\\ sig(clip) - apply sigma clipping algorythm to each pixel;\\ avsig(clip) - apply sigma clipping algorythm together with minmax rejection;\\ For more details about the various methods, please refer to Chapter Direct Imaging in Volume B of the ESO-MIDAS Users' Guide.\\ Before the combining is done the exposure type descriptors of the input frame are compared with the descriptor type stored in the keyword `exp'_TYP. In case this keyword is filled with `*' or `?' all exposure types are allowed. Else, a fatal error will follow if the the keyword content is not equal to one or more frame exposure types. The first and second element of descriptor LHCUTS, containing the real minimum and maximum of the frame are updated. In addition, the descriptor MEAN, MODE and MEDIAN contain the corresponding values of the pixels values within the area defined by the keyword IM_SEC, the useful image section.\\ To generate the output combined frame only those input pixels will be used that have intensities within the range stored in the keyword `exp'_RAN. The sigma frame, if created, also has the rejected pixels excluded.\\ In case the mmedian method is used the interval for averaging has to be specified by the `exp'_CLP keyword. This method does the same as in AVERAG/IMAGE using options=median,low,high. For further informations please refer to this help-page. Negative `exp'_CLP values indicate index intervals. In case the keyword `exp'_SIG is set two additional frame will be created: one containing the number of frames used for the combining result; a second contains the standard deviation around the mean result. \on\see See also: SET/CCD, SHOW/CCD, AVERAGE/IMAGE, AVERAGE/WINDOW \ees\exs Examples: \ex COMBINE/CCD ff ost_asso.tbl Create all master flat frames which names are stored the master flat column in the table ost_assoc.tbl. \xe\ex COMBINE/CCD bs myflats.cat Created the combined flat from all the frames in the catalogue myflats. \xe\ex COMBINE/CCD bs myflat1,myflat1,myflat2 Created the combined flat from the three input frames. \xe\ex COMBINE/CCD bs Combine bias frames. The input in taken from the keyword CCD_IN. Depending on the input continue like in one the above example. \xe \sxe