The muse_flat recipe =============================================================== .. data:: muse_flat Synopsis -------- Combine several separate flat images into one master flat file, trace slice locations, and locate dark pixels. Description ----------- This recipe combines several separate flat-field images into one master flat-field file and traces the location of the slices on the CCD. The master flat contains the combined pixel values of the raw flat exposures, with respect to the image combination method used, normalized to the mean flux. The trace table contains polynomials defining the location of the slices on the CCD. Processing trims the raw data and records the overscan statistics, subtracts the bias (taking account of the overscan, if --overscan is not "none"), and optionally, the dark from each raw input image, converts them from adu to count, scales them according to their exposure time, and combines the exposures using input parameters. To trace the position of the slices on the CCD, their edges are located using a threshold method. The edge detection is repeated at given intervals thereby tracing the central position (the mean of both edges) and width of each slit vertically across the CCD. Deviant positions of detections on CCD rows can be detected and excluded before fitting a polynomial to all positions measured for one slice. The polynomial parameters for each slice are saved in the output trace table. Finally, the area between the now known slice edges is searched for dark (and bright) pixels, using statistics in each row of the master flat. Constructor ----------- .. method:: cpl.Recipe("muse_flat") :noindex: Create an object for the recipe muse_flat. :: import cpl muse_flat = cpl.Recipe("muse_flat") Parameters ---------- .. py:attribute:: muse_flat.param.nifu IFU to handle. If set to 0, all IFUs are processed serially. If set to -1, all IFUs are processed in parallel. (int; default: 0) [default=0]. .. py:attribute:: muse_flat.param.overscan If this is "none", stop when detecting discrepant overscan levels (see ovscsigma), for "offset" it assumes that the mean overscan level represents the real offset in the bias levels of the exposures involved, and adjusts the data accordingly; for "vpoly", a polynomial is fit to the vertical overscan and subtracted from the whole quadrant. (str; default: 'vpoly') [default="vpoly"]. .. py:attribute:: muse_flat.param.ovscreject This influences how values are rejected when computing overscan statistics. Either no rejection at all ("none"), rejection using the DCR algorithm ("dcr"), or rejection using an iterative constant fit ("fit"). (str; default: 'dcr') [default="dcr"]. .. py:attribute:: muse_flat.param.ovscsigma If the deviation of mean overscan levels between a raw input image and the reference image is higher than |ovscsigma x stdev|, stop the processing. If overscan="vpoly", this is used as sigma rejection level for the iterative polynomial fit (the level comparison is then done afterwards with |100 x stdev| to guard against incompatible settings). Has no effect for overscan="offset". (float; default: 30.0) [default=30.0]. .. py:attribute:: muse_flat.param.ovscignore The number of pixels of the overscan adjacent to the data section of the CCD that are ignored when computing statistics or fits. (int; default: 3) [default=3]. .. py:attribute:: muse_flat.param.combine Type of combination to use (str; default: 'sigclip') [default="sigclip"]. .. py:attribute:: muse_flat.param.nlow Number of minimum pixels to reject with minmax (int; default: 1) [default=1]. .. py:attribute:: muse_flat.param.nhigh Number of maximum pixels to reject with minmax (int; default: 1) [default=1]. .. py:attribute:: muse_flat.param.nkeep Number of pixels to keep with minmax (int; default: 1) [default=1]. .. py:attribute:: muse_flat.param.lsigma Low sigma for pixel rejection with sigclip (float; default: 3.0) [default=3.0]. .. py:attribute:: muse_flat.param.hsigma High sigma for pixel rejection with sigclip (float; default: 3.0) [default=3.0]. .. py:attribute:: muse_flat.param.scale Scale the individual images to a common exposure time before combining them. (bool; default: True) [default=True]. .. py:attribute:: muse_flat.param.normalize Normalize the master flat to the average flux (bool; default: True) [default=True]. .. py:attribute:: muse_flat.param.trace Trace the position of the slices on the master flat (bool; default: True) [default=True]. .. py:attribute:: muse_flat.param.nsum Number of lines over which to average when tracing (int; default: 32) [default=32]. .. py:attribute:: muse_flat.param.order Order of polynomial fit to the trace (int; default: 5) [default=5]. .. py:attribute:: muse_flat.param.edgefrac Fractional change required to identify edge when tracing (float; default: 0.5) [default=0.5]. .. py:attribute:: muse_flat.param.losigmabadpix Low sigma to find dark pixels in the master flat (float; default: 5.0) [default=5.0]. .. py:attribute:: muse_flat.param.hisigmabadpix High sigma to find bright pixels in the master flat (float; default: 5.0) [default=5.0]. .. py:attribute:: muse_flat.param.samples Create a table containing all tracing sample points. (bool; default: False) [default=False]. .. py:attribute:: muse_flat.param.merge Merge output products from different IFUs into a common file. (bool; default: False) [default=False]. The following code snippet shows the default settings for the available parameters. :: import cpl muse_flat = cpl.Recipe("muse_flat") muse_flat.param.nifu = 0 muse_flat.param.overscan = "vpoly" muse_flat.param.ovscreject = "dcr" muse_flat.param.ovscsigma = 30.0 muse_flat.param.ovscignore = 3 muse_flat.param.combine = "sigclip" muse_flat.param.nlow = 1 muse_flat.param.nhigh = 1 muse_flat.param.nkeep = 1 muse_flat.param.lsigma = 3.0 muse_flat.param.hsigma = 3.0 muse_flat.param.scale = True muse_flat.param.normalize = True muse_flat.param.trace = True muse_flat.param.nsum = 32 muse_flat.param.order = 5 muse_flat.param.edgefrac = 0.5 muse_flat.param.losigmabadpix = 5.0 muse_flat.param.hisigmabadpix = 5.0 muse_flat.param.samples = False muse_flat.param.merge = False You may also set or overwrite some or all parameters by the recipe parameter `param`, as shown in the following example: :: import cpl muse_flat = cpl.Recipe("muse_flat") [...] res = muse_flat( ..., param = {"nifu":0, "overscan":"vpoly"}) .. seealso:: `cpl.Recipe `_ for more information about the recipe object. Bug reports ----------- Please report any problems to `Peter Weilbacher (based on Joris Gerssen's draft) `_. Alternatively, you may send a report to the `ESO User Support Department `_. Copyright --------- This file is part of the MUSE Instrument Pipeline Copyright (C) 2005, 2019 European Southern Observatory This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02111-1307 USA .. codeauthor:: Peter Weilbacher (based on Joris Gerssen's draft)