# @(#)long.hlp 17.1.1.1 (ESO) 01/25/02 17:28:22 #+++++++++++++++++++++++++++++++++++++++++++++++++++++++ #.COPYRIGHT (C) 1993 European Southern Observatory #.IDENT long.hlp #.AUTHORS Pascal Ballester (ESO/Garching) # Cristian Levin (ESO/La Silla) #.KEYWORDS Spectroscopy, Long-Slit #.PURPOSE # This is the help file for the extended help # feature of XLong. # #.VERSION 1.0 Package Creation 17-MAR-1993 #------------------------------------------------------- # ~HELP_CONTEXT This is the context Long. ~HELP_HELP You can get an extended help for each button of the interface by pressing the right mouse button when the cursor is over the interface button. ~HELP_TUTORIAL Not available for the moment. ~HELP_VERSION This is the beta version of the new context Long. ~MAIN_SEARCH Open the search lines interface. ~MAIN_IDENT Open the interface that allows identification of comparison lines. The line catalogue is listed in the main window. More information is given with the individual buttons in the interface. PARAMETERS: the following parameters are required by interface: a) Line catalogue -- name of the file containing the wavelength of the comparison lines. b) Wavelength range -- select the range of wavelengths from the line table to be used in the calibration. c) Strength limit -- select the minimum intensity of the comparison lines to be used in the calibration. d) Starting line -- row number where the lines will be identified. ~MAIN_CALIB Open the wavelength calibration interface. ~MAIN_REBIN Open the rebinning interface. ~MAIN_EXTRACT Open the spectrum extraction interface. It contains commands for fitting the sky and extracting the spectra of unresolved sources using an optimization algorithm. ~MAIN_FLUX Open the flux calibration interface. ~MAIN_BATCH Open the batch reduction form. ~SEARCH_SEARCH Automatic search of 2-D spectra for the positions of the spectral lines. The interface offers three algorithms for determining the centroids: gravity -- Find the center of gravity of the lines. gaussian -- Fit a gaussian to the line profiles. maximum -- Use the pixel with the maximum intensity. If you click the left buitton of the mouse, the list of .bdf files appears. Click the file you want to search. The identifier of the file is displayed in the main window. PARAMETERS: the following parameters are required by search: a) Threshold -- to define the level above which lines are identified b) Width of search window -- to search and center the lines. c) Smooth Factor -- search averaging N rows above and N rows below every line (except at borders). Thus a smoothing of 2xN+1 rows is applied. d) Binning step -- ~SEARCH_PLOT Plot the found lines ~CALIB_CALIBRATE Determine the dispersion relation for the starting row using the identified lines (mode IDENT) or a previous session (mode GUESS) as initial guesses. The program iterates until all lines within the given tolerance are identified. The number of lines found and the final rms of the fit are given. The iterative identification of lines is controlled by the matching parameter (alpha). For each element of the table line a computed wavelength is estimated. The closest wavelength in the line catalog will be the identification candidate. The absolute difference between the computed wavelength and the candidate wavelength is the residual. The residual divided by alpha is the acceptation distance. The distance of four neighbours is taken into account (left and right in the line table and in the line catalog). The candidate is retained if the distance of the closest of the four neighbours is larger than the the acceptation distance. The optimal range for the matching parameter alpha is between 0. and 0.5, which secures that the candidates will be retained only if the neighbours are at least twice further (alpha=0.5) than the residual. The maximal deviation is expressed in pixels. The iterative process aborts if the fit rms in pixels after line identification is larger than the maximal deviation. A typical value for this parameter is 10 pixels. ~CALIB_EDIT Add or subtract lines from the fit. Use the "Dispersion" or "Spectrum" button to display the fit. Click "edit". Position the graphics cursor on top of the line you want to edit (eliminate or reset. In colour displays, the line symbol will turn red when eliminated and green or blue again when reset). The button "Calibrate" should be used to update the fit after editing points. ~CALIB_GETCUR Read the wavelength of any feature with the graphics cursor. The values of the pixel position and the corresponding wavelength are displayed in the MIDAS window. This command is designed to be used with the "Spectrum" command. ~CALIB_ALL It propagates the polynomial fits from the initial line to the whole spectrum row-by-row. ~CALIB_TWICE The row-by-row calibration is done in two passes in such a way that the same set of lines is used in all rows. Thus, this option uses only the lines that have been found in all the rows of the spectrum. ~CALIB_DISPER Plot delta lambda vs. lambda for all lines found. ~CALIB_RESID Plot the fit residuals vs. lambda. ~CALIB_SPEC Plot the spectrum labeling the lines with their table wavelengths. ~CALIB_SHAPE Plot the distortion of the spectrum from a specific wavelength value. ~REBIN_RBR Rebin the spectrum to wavelength. Calibration must be done before to determine the polynomial coefficients. This pulldown menu offers three options: LINEAR -- Rebins using linear interpolation. Flux is preserved. QUADRATIC -- Rebins using quadratic interpolation. Flux is preserved. SPLINE -- Rebins using spline interpolation. Flux is not preserved. After clicking the desired method LONG prompts for the file to be rebinned and the name of the output file. ~REBIN_2D ~REBIN_TABLE ~REBIN_PLOT ~EXTRACT_SKY Asks the user for the sky windows using the cursor over the display window. The coordinates are then displayed in the input form. ~EXTRACT_OBJECT Asks the user for the object limits using the cursor over the display window. The coordinates are then displayed in the input form. ~EXTRACT_FIT Fit a polynomial to the data in two windows along the Y-axis. Two modes can be selected: Same spatial profile -- Here it is assumed that the normalized spatial profile is the same for all columns and only one polynomial is fitted to the mean spatial profile. Independent profile -- In this case an independent polynomial is fitted for every row of the spectrum, filtering also the cosmic rays. PARAMETERS: The following parameters must be set in the input form: a) Sky limits (pixels) -- starting and ending Y coordinates of the sky windows b) Polynomial fit degree -- degree of the fit to be used. c) Radius -- used for cosmics rays rejection. ~EXTRACT_AVERAGE The standard method. The sky is taken from the sky limits values of the input window. The result is summed or averaged depending on the extraction method parameter. ~EXTRACT_WEIGHT Extract spectrum from CCD frame. The rows of the spectrum are added with weights which are chosen for optimal S/N-ratio of the resulting spectrum. Cosmic ray hits are removed by analyzing the profile perpendicular to the dispersion (assumed to be along the X-axis). The method is only suited for spectra of (spatially) unresolved sources. The method is very similar to the one described by Horne (1986, PASP 98, 609). PARAMETERS: The extraction algorithm uses the following parameters: a) Object limits (pixels) -- Approximate Y coordinates of the object (starting and ending). b) Extraction iterations -- Number of iterations in the extraction process. c) Read-out-noise (e-) -- Read out noise of the CCD in electrons. d) Inverse gain factor -- Conversion factor from ADU to electrons. (e-/ADU) e) Threshold for cosmic rays -- Threshold used for the rejection of cosmic ray hits. ~FLUX_EXTIN Determine the extinction curve by interpolating the standard extinction tables for La Silla. This table must be in the working directory and can be copied from the MIDAS database using a button in the "utils" pulldown menu. The airmass must be given. If present, the airmass in the file header is used as default. In the present version, the airmass correction can only be applied to 1-D spectra. ~FLUX_INTEGR Bin the standard star spectrum to the bands of the calibration tables and produce the calibration curve. ~FLUX_FIT This command allows to fit the calibration curve depending on the fitting selected: polynomial -- the fit degree of the input form is used. spline -- Standard spline fits. The parameters of the spline must be given in the input form (smooth factor, degree). ~EDIT_FLUX This command allows to edit the points generated by the integration process. ~FLUX_CORRECT Calibrate the input image in flux, using the response curve generated. ~FLUX_FILTER ~FLUX_PFLUX Plot the flux table. ~FLUX_PRESP Plot the response curve.