MUSE Pipeline Reference Manual  2.1.1
Data Structures | Typedefs
Recipe muse_twilight: Combine several twilight skyflats into one cube, compute correction factors for each IFU, and create a smooth 3D illumination correction.

Data Structures

struct  muse_twilight_params_s
 Structure to hold the parameters of the muse_twilight recipe. More...
 

Typedefs

typedef struct muse_twilight_params_s muse_twilight_params_t
 Structure to hold the parameters of the muse_twilight recipe. More...
 

Detailed Description

Author
Peter Weilbacher
  Processing first handles each raw input image separately: it trims the
  raw data and records the overscan statistics, subtracts the bias (taking
  account of the overscan, if --overscan is not "none"), converts the
  images from adu to count, subtracts the dark, divides by the flat-field
  and combines all the exposures using input parameters.

  The input calibrations geometry table, trace table, and wavelength
  calibration table are used to assign 3D coordinates to each CCD-based
  pixel, thereby creating a pixel table from the master sky-flat. These
  pixel tables are then cut in wavelength using the --lambdamin and
  --lambdamax parameters. The integrated flux in each IFU is computed as
  the sum of the data in the pixel table, and saved in the header, to be
  used later as estimate for the relative throughput of each IFU.

  If an ILLUM exposure was given as input, it is then used to correct the
  relative illumination between all slices of one IFU. For this, the data
  of each slice within the pixel table of each IFU is multiplied by the
  normalized median flux of that slice in the ILLUM exposure.

  The pixel tables of all IFUs are then merged, using the integrated
  fluxes as inverse scaling factors, and a cube is reconstructed from the
  merged dataset, using given parameters. A white-light image is created
  from the cube. This skyflat cube is then saved to disk, with the
  white-light image as one extension.

  To construct a smooth 3D illumination correction, the cube is
  post-processed in the following way: the white-light image is used to
  create a mask of the illuminated area. From this area, the optional
  vignetting mask is removed. The smoothing is then computed for each
  plane of the cube: the illuminated area is smoothed (by a 5x7 median
  filter), normalized, fit with a 2D polynomial (of given polynomial
  orders), and normalized again.
  A smooth white image is then created by collapsing the smooth cube.

  If a vignetting mask was given, the corner area given by the mask is
  used to compute a 2D correction for the vignetted area: the original
  unsmoothed white-light image is corrected for large scale gradients by
  dividing it with the smooth white image. The residuals in the corner
  area then smoothed using input parameters. This smoothed vignetting
  correction is the multiplied onto each plane of the smooth cube,
  normalizing each plane again.

  This twilight cube is then saved to disk.

Typedef Documentation

Structure to hold the parameters of the muse_twilight recipe.

This structure contains the parameters for the recipe that may be set on the command line, in the configuration, or through the environment.