MUSE_WAVECAL(7)

💫 muse_wavecal — a manual page, but make it bestie muse_wavecal(7) ✨

okay so. sit down, grab a snack, because we're doing the muse recipes thing and honestly? this one's a bop. it's muse_wavecal, section 7 of your manual, and it's about figuring out what wavelength each lil pixel actually corresponds to. very main character. let's go 💅

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🌈 NAME 🌈

muse_wavecal — detect arc emission lines and determine the wavelength solution for each slice. that's the whole vibe. arc lines in, wavelength solution out, one solution per slice. slay.

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✨ SYNOPSIS ✨

esorex muse_wavecal [OPTIONS] FILE.sof

that's it. that's the summoning ritual. 🕯️

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🦋 DESCRIPTION 🦋

so this recipe detects arc emission lines and fits a wavelength solution to each slice of the instrument. the wavelength calibration table is where the polynomials live — the ones that define the wavelength solution of the slices on the CCD. no cap.

here's the pipeline journey, step by step, no skips:

• processing trims the raw data and records the overscan statistics
• then it subtracts the bias — and yes, it takes account of the overscan, but only if --overscan is not "none"
• then it converts them from adu to count
• optionally the dark can be subtracted and the data can be divided by the flat-field, but this is not recommended. fr fr, don't.
• the data is then combined, using input parameters, into separate images for each lamp

now for the wavelength solution part, which is the whole point:

• arc lines are detected at the center of each slice — using threshold detection on a S/N image
• then they're assigned wavelengths, using pattern matching to identify lines from the input line catalog
• each line is then traced to the edges of the slice, using Gaussian centering in each CCD column
• the Gaussians don't just give you center — they also give you centering error and line properties (e.g. FWHM). obsessed with a multi-purpose gaussian honestly
• deviant fits are detected using polynomial fits to each arc line (using the xorder parameter) and then rejected
• these analysis and measuring steps are carried out separately on images exposed by the different arc lamps, which reduces the amount of blending that can otherwise mess with line identification and Gaussian centering. smart. iconic.
• the final two-dimensional fit uses all positions (of all lamps), their wavelengths, and the given polynomial orders to compute the final wavelength solution for each slice, iteratively rejecting outliers
• and this final fit can be either unweighted (fitweighting="uniform", for fastest processing) or weighted (any other value of fitweighting, for higher accuracy)

so like… choose your fighter: speed or precision. both valid. 🫶

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🎀 OPTIONS 🎀

one bullet per option, bestie, because we don't gatekeep flags here. also: the full name for the EsoRex configuration file is given for each one, because that's how you set these outside the command line. iykyk.

• --nifu <int> — IFU to handle. if you set it to 0, all IFUs are processed serially. if you set it to -1, all IFUs are processed in parallel. (int; default: 0). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.nifu [default = 0].
• --overscan <str> — how the overscan gets treated. if this is "none", stop when detecting discrepant overscan levels (see ovscsigma). if it's "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. if it's "vpoly", a polynomial is fit to the vertical overscan and subtracted from the whole quadrant. (str; default: ´vpoly´). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.overscan [default = vpoly].
• --ovscreject <str> — this influences how values are rejected when computing overscan statistics. your options are: no rejection at all ("none"), rejection using the DCR algorithm ("dcr"), or rejection using an iterative constant fit ("fit"). (str; default: ´dcr´). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.ovscreject [default = dcr].
• --ovscsigma <float> — the vibes-check threshold. 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 the sigma rejection level for the iterative polynomial fit — and 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). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.ovscsigma [default = 30.0].
• --ovscignore <int> — 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). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.ovscignore [default = 3].
• --combine <str> — type of lampwise image combination to use. (str; default: ´sigclip´). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.combine [default = sigclip].
• --lampwise <bool> — identify and measure the arc emission lines on images separately for each lamp setup. (bool; default: True). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.lampwise [default = True].
• --sigma <float> — sigma level used to detect arc emission lines above the median background level in the S/N image of the central column of each slice. (float; default: 1.0). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.sigma [default = 1.0].
• --dres <float> — the allowed range of resolutions for pattern matching (of detected arc lines to line list), in fractions relative to the expected value. (float; default: 0.05). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.dres [default = 0.05].
• --tolerance <float> — tolerance for pattern matching (of detected arc lines to line list). (float; default: 0.1). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.tolerance [default = 0.1].
• --xorder <int> — order of the polynomial for the horizontal curvature within each slice. (int; default: 2). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.xorder [default = 2].
• --yorder <int> — order of the polynomial used to fit the dispersion relation. (int; default: 6). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.yorder [default = 6].
• --linesigma <float> — sigma level for iterative rejection of deviant fits for each arc line within each slice. a negative value means to use the default (2.5). (float; default: -1.0). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.linesigma [default = -1.0].
• --residuals <bool> — create a table containing residuals of the fits to the data of all arc lines. this is useful to assess the quality of the wavelength solution in detail. (bool; default: False). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.residuals [default = False].
• --fitsigma <float> — sigma level for iterative rejection of deviant datapoints during the final polynomial wavelength solution within each slice. a negative value means to use the default (3.0). (float; default: -1.0). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.fitsigma [default = -1.0].
• --fitweighting <str> — type of weighting to use in the final polynomial wavelength solution fit, using centroiding error estimate and/or scatter of each single line as estimates of its accuracy. (str; default: ´cerrscatter´). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.fitweighting [default = cerrscatter].
• --saveimages <bool> — save. (bool; default: False). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.saveimages [default = False].
• --resample <bool> — resample the input arc images onto 2D images for a visual check using tracing and wavelength calibration solutions. > heads up bestie: the image produced will show small wiggles even when the calibration was successful! do not panic. the wiggles are not a red flag. 💀 (bool; default: False). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.resample [default = False].
• --wavemap <bool> — create a wavelength map of the input images. (bool; default: False). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.wavemap [default = False].
• --merge <bool> — merge output products from different IFUs into a common file. (bool; default: False). the full name of this option for the EsoRex configuration file is muse.muse_wavecal.merge [default = False].

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also note: 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. go read it, it's right there. 🫶

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okay that's the first chunk, we're not done yet — more of this page is coming, don't go anywhere 💖

📜 LICENSE 📜

okay bestie, legal time, but make it cute ✨ This file is part of the MUSE Instrument Pipeline — Copyright (C) 2005, 2019 European Southern Observatory. That's the whole vibe. They made it, they own it, we love them for it. 💜

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. So like, v2 or v2-plus, your call, slay. 💅

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. Yeah bestie, no warranty, not even the implied ones — read 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. Snail mail era, iconic fr fr. 🎀

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and that's a wrap on the whole page, bestie 🫶 no cap — this one's from muse_wavecal, version 2.8.7, and it's filed under MUSE_WAVECAL(7) in the manual pages. Go forth and calibrate those wavelengths, you absolute main character. 🌈💖✨🦋🌸