fors_normalise_flat7

Usage

Overview

This recipe is used to normalise a master flat field frame dividing it by its large scale illumination trend. This recipe can be applied both to generic multi-slit (MOS/MXU) and to long slit exposures (either LSS, or LSS-like MOS/MXU), even if different normalisation methods are applied in such different cases. The input master flat field image is the product of the recipe fors_flat. The input spectral curvature table, product of the recipe fors_detect_spectra, is only required in the case of multi-slit data.

In the case of multi-slit data, the flat field spectra are spatially rectified, heavily smoothed, and then mapped back on the CCD. Then the master flat image is divided by its smoothed counterpart. The smoothing may be obtained either by applying a running median filter of specified sizes, or by polynomial fitting along the dispersion direction performed independently for each row of the spatially remapped spectra.

In the case of long-slit data, the smoothing can still be obtained either by applying a running median filter or by polynomial fitting, but the polynomial fitting will be performed along the spatial direction, for each column of the spectrum.

In the table below the MXU acronym can be alternatively read as MOS or LSS.

Input files:

DO category: Type: Explanation: Required:
MASTER_SCREEN_FLAT_MXU Calib Master flat frame Y
DISP_COEFF_MXU Calib Wavelength calibration Y
CURV_COEFF_MXU Calib Spectral curvature .

SLIT_LOCATION_MXU Calib Slit detection .

GRISM_TABLE Calib Grism table Y

Output files:

DO category: Data type: Explanation:
MASTER_NORM_FLAT_MXU FITS image Normalised flat field

Options

--dispersion <float>

Expected spectral dispersion (Angstrom/pixel) (float; default: 0.0). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.dispersion [default = 0.0].

--startwavelength <float>

Start wavelength in spectral extraction (float; default: 0.0). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.startwavelength [default = 0.0].

--endwavelength <float>

End wavelength in spectral extraction (float; default: 0.0). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.endwavelength [default = 0.0].

--spa_polydegree <int>

Polynomial degree for the flat field fitting along spatial direction (int; default: -1). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.spa_polydegree [default = -1].

--sradius <int>

Smooth box radius for flat field along spatial direction (used if spa_knots < 0) (int; default: 10). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.sradius [default = 10].

--disp_nknots <int>

Number of knots in flat field fitting splines along dispersion direction (int; default: -1). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.disp_nknots [default = -1].

--dradius <int>

Smooth box radius for flat field along dispersion direction (if disp_knots < 0) (int; default: 10). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.dradius [default = 10].

--splfit_threshold <float>

Threshold percentage for flat spline fittingwith respect to the maximum (float; default: 0.01). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.splfit_threshold [default = 0.01].

Note that it is possible to create a configuration file containing these options, along with suitable default values. Please refer to the details provided by the 'esorex --help' command.

Version

fors_normalise_flat 5.5.6