ESO's Fibre-fed, Extended Range,
(FEROS) is a bench-mounted, thermally controlled,
prism-crossdispersed échelle spectrograph.
It is designed to be a high
resolution (R~48,000), high efficiency (20%), versatile spectrograph
providing in a
single spectrogram almost complete
spectral coverage from ~350nm to ~920nm. The mechanical and thermal
stability of FEROS allow for a precise wavelength calibration based on
daytime calibrations and for most purposes additional calibrations
during the night are not necessary, thus ensuring a high productivity
in terms of scientific data produced. Although not intended as a
`radial velocity machine', precise radial velocity
work (accuracies of ~25m/s or better) is also possible, especially via
Object-Calibration mode. Extremely high precision Radial Velocity work
(~1m/s) is better done using HARPS which
also has higher resolution (R~115,000). Extremely high resolution
work (upto R~235,000) is better done with CES.
FEROS is fed by two fibres providing simultaneous spectra of OBJECT
plus either SKY or one of the two CALIBRATION lamps (wavelength
calibration and flat-field). The fibres are illuminated via 2.0 arcsec
apertures on the sky separated by 2.9 arcmins. A small amount of
rotation of the telescope adapter is possible in the rare case that a
field star by chance falls on the sky fibre. The resolving power of
48,000 achieved with a two-slice image slicer over the spectral range
of ~350nm to ~920nm spread over 39 échelle orders. The detector
EEV 2k×4k CCD.
A dedicated pipeline implemented as a MIDAS context provides, in almost
realtime, extracted 1-dimensional, wavelength calibrated spectra
which can be used as a quicklook to check S/N etc. The core of
the FEROS pipeline is included in the standard MIDAS distribution and
together with the FEROS-DRS package
can be used to re-reduce the data to obtain publication quality results.
Calibration lamp light is delivered to the SCIENCE fibres in the FEROS
Fibre Head via the CALIBRATION fibres from the FEROS Calibration Unit.
Both FEROS and
are now permanently mounted at the
telescope. Switching from one instrument to the other is a simple
matter of moving the M3 and takes just 8 seconds.