Changes

For arcs, automatic wavelength calibration is attempted. The accuracy of this is appropriate for the spirit of a quick look tool and is typically ~2A. This allows the observer to check that the wavelength range of interest is being covered and to identify spectral features in science spectra. This is not intended to be a final science-quality level reduction and there are a number of caveats on the extraction and calibration process listed below. However, for some users, this may be entirely sufficient for their science needs. Even if it is not precise enough, it can be used as a starting point for a more careful reduction and notes on this are given belowhere https://topswiki.saao.ac.za/index.php/Using_QL_outputs.

The profile pane shows a cross section in the spatial direction through the spectrum. This controls the regions used for extraction and sky subtraction of the science data. The default is to search for the '''highest peak''' in the spectrum automatically and to fit a region +/-2 sigma around a Gaussian fit to this peak. An alternative is to choose the '''most central peak''', assuming observers try to centre the object within this slit. This setting is useful when a brighter object than the intended target also falls within the slit. If neither of these settings is suitable, the user may '''manually''' identify the extraction region using the extraction window sliders below the plot window and clicking '''"Update with Manual Settings"''' to apply the changes. To return back to auto extraction, simply select the '''Auto''' radio button. Note: there may be a small delay after adjusting any of these, since the software is recalculating the extracted spectrum and updating all the plot windows in real-time.

Similarly, the side bands used to identify the sky may be tweaked interactively. The regions are not allowed to cross the extraction region, nor to fall outside of the cyan slit boundary. If one of the regions is contaminated by another object, it may be deselected using the check box below the bandslider.

Finally, for an arc, most of these options are disabled. The '''arc extraction''' simply uses the '''single row''' at the mid point between the two cyan extraction edge lines. This single row extraction : minimises the potential impact of cosmic rays; the broadening of lines by summing over the tilted lines in the full window; and should provide sufficient S/N with even short exposures.

If the spectrum is labelled as an '''arc''' in the header, the QL tool will attempt to perform automated wavelength calibration. This is generally robust and no changes of settings should be needed. For the less frequently used gratings or for unusual grating angles, the default parameters may not work so well, and so notes for advanced users to change settings to the fitting routine are provided ZZZhere https://topswiki.saao.ac.za/index.php/Quick_Look_Tool#WLC_advanced_tab .After wavelength calibration of an arc, a '''library reference spectrum''' will be overplotted in green allowing the user to quickly check the quality of the calibration. As mentioned in the introduction, this is intended to be a quick look calibration at the ~2A level and solutions should must be refined by the user if greater precision is needed to meet the science requirements. As a further aid, the wavelength of the midpoint of the spectrum is printed to the bottom of the screen, allowing the observer to monitor any possible drifts in the wavelength coverage.

The default files to produce (if the appropriate check boxes have not been unchecked in the QL GUI) are a '''1D ascii file''' and a '''1D extracted FITS spectrum''', a0161390'''a0161390_1D_1D.txt''' and a0161390'''a0161390.ms.fits''' respectively, for an input image named a0161390.fits. Both of these contain the same data, just in a different format depending on the user's preference. Additionally, a log recording the extraction settings used is stored in a0161390'''a0161390.json'''. This last file is probably not of interest to most users.

'''wavelen objCounts skyAndBiasCounts'''

* If the file has been wavelength calibrated, the first column contains the wavelength in A, one line per pixel number. Otherwise the first column will be pixel number (i.e. just running number from 1 to Npixels).

* The second column is the counts in the extraction aperture after sky subtraction (if selected). Note: this is always '''summed counts within the aperture''', even if another extraction option (such as peak counts) is selected.

* The third column contains the '''counts per pixel''' from the sky aperture(s). If sky subtraction has been unselected, these will be 0.

The .json file contains a log of the settings of parameters used in the extraction. It may be of interest to users wishing to write their own code for taking these extractions as a starting point, or to users as a double check of which arc was used to wavelength calibrate their data("currArc").

'''Please don't modify software without discussing and clearing the modification with the software developers or instrument PI.''' To edit the '''bounds of the 2D spectrum''' (cyan lines in 2D plot window) edit as root the following file: