Since the FLOYDS spectrographs are mounted on the 2m telescopes’ Cassegrain rotator stages, the slit may be oriented along any desired position angle on the sky (note that this is not necessarily a good idea, though, given the very broad wavelength coverage of FLOYDS; we generally recommend orienting the slit along the parallactic angle). An Andor Newton 940 CCD controller package, with an e2V 42-10 CCD (13.5 $$\mu$$m pixels and a 2048$$\times$$512 format), is used with a broadband ultraviolet-enhanced coating. The CCD package is thermo-electrically cooled to -70 C, with negligible dark current. Spectra do fringe above $$\sim$$700 nm, but this can be corrected when a flat field is taken at the same position as a science frame.

Wavelength calibration is accomplished with a Mercury Argon (HgAr) lamp, and flat fielding with a combination of a tungsten-halogen and high-powered xenon lamp (whose light are combined with a dichroic). The calibration unit housing these lamps sits in a cabinet near the telescope with a fiber connection to FLOYDS. A deployable arm in the FLOYDS instrument can direct light from the calibration unit into the spectrograph, and accompanying optics delivers light with an f/10 beam, mimicking the actual Faulkes telescopes. A typical calibration arc is shown in Fig. \ref{fig:arc}, and a representative flat is shown in Fig. \ref{fig:flat}