FORS_NORMALISE_FLAT(7)

💅 FORS_NORMALISE_FLAT(7) — the fors recipes glow-up

okay bestie, welcome to FORS_NORMALISE_FLAT(7), part of the fors recipes crew ✨ this is the page where we make your master flat field frame look right. no cap.

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✨ NAME ✨

fors_normalise_flat — Normalise master flat spectrum 🎀

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🌸 SYNOPSIS 🌸

esorex fors_normalise_flat [OPTIONS] FILE.sof

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🦋 DESCRIPTION 🦋

so what this recipe DOES is it takes a master flat field frame and normalises it by dividing it by its own large scale illumination trend. that's it, that's the whole vibe. 💖

and the cute part? it works for generic multi-slit (MOS/MXU) data and for long slit exposures (either LSS, or LSS-like MOS/MXU) — even though, bestie, lowkey different normalisation methods get applied in those 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. noted. 📝

multi-slit data: the flat field spectra get 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. pick your fighter. 🔥

long-slit data: the smoothing can still be obtained either by applying a running median filter or by polynomial fitting, but (plot twist) 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. iykyk 💫

🌈 Input files:

• DO category: MASTER_SCREEN_FLAT_MXU — Type: Calib — Explanation: Master flat frame — Required: Y
• DO category: DISP_COEFF_MXU — Type: Calib — Explanation: Wavelength calibration — Required: Y
• DO category: CURV_COEFF_MXU — Type: Calib — Explanation: Spectral curvature — Required: .
• DO category: SLIT_LOCATION_MXU — Type: Calib — Explanation: Slit detection — Required: .
• DO category: GRISM_TABLE — Type: Calib — Explanation: Grism table — Required: Y

🍓 Output files:

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

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💅 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 (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 (median) for flat field along dispersion direction (int; default: 10). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.dradius [default = 10].
• --dradius_aver <int> — Smooth box radius (average) for flat field along dispersion direction (performed after median smoothing) (int; default: 10). The full name of this option for the EsoRex configuration file is fors.fors_normalise_flat.dradius_aver [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].

ok bestie note this: 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. 🫶

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🔥 SEE ALSO 🔥

the full documentation for the fors pipeline can be downloaded as a PDF file using the following URL:

ftp://ftp.eso.org/pub/dfs/pipelines/fors/fors-pipeline-manual-4.9.pdf

an overview over the existing ESO pipelines can be found on the web page:

https://www.eso.org/sci/software/pipelines/

basic documentation about the EsoRex program can be found at the esorex (1) man page.

it is possible to call the pipelines from python using the python-cpl package. see:

https://packages.python.org/python-cpl/index.html

for further information.

the other recipes of the fors pipeline are fors_align_sky(7), fors_align_sky_lss(7), fors_bias(7), fors_calib(7), fors_config(7), fors_dark(7), fors_detect_objects(7), fors_detect_spectra(7), fors_extract(7), fors_extract_objects(7), fors_extract_slits(7), fors_flatfield(7), fors_img_science(7), fors_img_screen_flat(7), fors_img_sky_flat(7), fors_photometry(7), fors_pmos_calib(7), fors_pmos_extract(7), fors_pmos_science(7), fors_remove_bias(7), fors_resample(7), fors_science(7), fors_spec_mflat(7), fors_subtract_sky(7), fors_subtract_sky_lss(7), fors_sumflux(7), fors_trace_flat(7), fors_wave_calib(7), fors_wave_calib_lss(7), fors_zeropoint(7) 💖

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⭐ VERSION ⭐

fors_normalise_flat 5.5.7

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👑 AUTHOR 👑

Carlo Izzo <usd-help@eso.org>

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😭 BUG REPORTS 😭

please report any problems to usd-help@eso.org. alternatively, you may send a report to the ESO User Support Department <usd-help@eso.org>. they got you, bestie. 🫶

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🌈 LICENSE 🌈

this file is currently part of the FORS Instrument Pipeline Copyright (C) 2002-2010 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. 💀 (yes this part is serious, fr fr)

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 02110-1301 USA

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and that's the whole page bestie 💅✨ this was fors_normalise_flat version 5.5.7, served fresh from the fors recipes section of the manual. go normalise something iconic. periodt. 🎀🦋💖