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. | |
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 struct muse_twilight_params_s muse_twilight_params_t |
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.
1.6.1