== Advanced config ==
=== Edges of 2D spectrum ===
To edit the '''bounds of the 2D spectrum''' (cyan lines in 2D plot window) edit as root the following file:
'''/usr/local/etc/qlgui/pars.json'''
The upper and lower bounds of the slit (which can be read off the 2D plot window using the cursor) are given by '''sl0''' and '''sl1''' respectively for the given grating name. e.g. for grating 5, the upper and lower bands are gr5_sl1 and gr5_sl0. Edit the numbers appropriately and resave the file. The changes should take effect the next time a spectrum is loaded.
=== WLC advanced tab ===
In rare cases, the automatic wavelength calibration may fail. The "WLC advanced" tab provides settings to tweak the method used in the fitting. The 2x2 grid of plots on the left show some useful diagnostics of the fitting.