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% @(#)mfit_roma.hlq 19.1 (ESO-IPG) 02/25/03 13:29:28
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MFIT/ROMAFOT 26-OCT-1989 RHW
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MFIT/ROMAFOT frame [int_tab] [thres,sky] [sig,sat,tol,iter] [meth,[beta]]
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[fit_opt] [mean_opt] [mod_file]
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determine characteristics of stellar images by non-linear fitting
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Purpose: Determine characteristics of stellar images by non-linear
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fitting. The integral of the PSF is computed over the pixel area.
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Syntax: MFIT/ROMAFOT frame [int_tab] [thres,sky] [sig,sat,tol,iter]
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[meth,[beta]] [fit_opt] [mean_opt] [mod_file]
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frame = input image frame
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int_tbl = name of the intermediate table which contains the
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selected objects; default is the frame name with
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thres,sky = photometric threshold and sky background. Data below the
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threshold will be ignored. Default values are those used
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in the commands SKY/ROMAFOT and indicated in FIND/ROMAFOT.
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sig,sat,tol,iter = trial value for sigma (parameter for the width of
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the Gaussian or Moffet curve), the saturation, the shift
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tolerance, and the maximum number of iterations for each
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each window. The defaults for sigma and saturation are
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the values used by previous commands (SKY/ROMAFOT); the
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default shift tolerance is 2 pixels, and for the number of
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meth,beta = non-linear fitting method to be used. One can choose
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between two fitting functions:\\
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GI: a Gaussian function with inverse prop. weighting;\\
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GU: a Gaussian function with uniform weighting;\\
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MI,number: Moffat function with inverse proportional
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weighting and with beta factor number;\\
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MU,number: Moffat function with uniform weighting and
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with beta factor number.\\
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The default is MU,4.0.
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fit_opt = four character logical string consisting of `Y'
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and `N', indicating which parameters should kept
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fixed. The meaning of the string is as follows:\\
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position 1: fix sigma;\\
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position 2: fix sky background;\\
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position 3: fix position;\\
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position 4: allow tilted plane.\\
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The default is `YNNN'.
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mean_opt = character indicating if mean values of previous
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windows should be used as trial values for the next.
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One can choose between:\\
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S: mean values for sigma should be used;\\
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B: mean values for sky background should be used;\\
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A: mean values for sigma and sky background should
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N: No mean values should be used as trials.\\
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mod_file = Data file containing the number of intervals over
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each pixel and according to the table created by
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MODEL/ROMAFOT. The file is assumed to have extension
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`.dat'. Default is that PSF function is estimated over
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a fixed 3x3 array over each pixel.
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Note: The difference between FIT/ROMAFOT and MFIT/ROMAFOT is that
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the former compares a given pixel to the value of the PSF at the
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centre of the pixel, the latter computes the integral of the PSF
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over the pixel area. The approximation used by FIT/ROMAFOT is
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good when the pixel size is small compared with the scale
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lenght of the point images.
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All the comments made for FIT/ROMAFOT hold for IFIT/ROMAFOT
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MFIT/ROMAFOT GCLUST1 GCLINTER
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Fit the windows in frame GCLUST1, stored in the intermediate table
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GCLINTER, using a maximum of 50 iteration (default). Start from
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the beginning in the table (default), and use a Moffat function
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with beta=4 (default).