The high-resolution FIbre-fed Echelle Spectrograph (FIES)

FIES is a cross-dispersed high-resolution echelle spectrograph with a maximum spectral resolution of R = 67000. The entire spectral range 370-730 nm is covered without gaps in a single, fixed setting. To isolate it from sources of thermal and mechanical instability, FIES is mounted in a heavily insulated building separate from and adjacent to the NOT dome.

The optical fibres that connect the telescope with the spectrograph are permanently mounted with a movable 45-degree mirror near the focal plane of the telescope. The fibres run from the instrument adapter through the telescope and azimuth axis to the spectrograph enclosure. Being a permanently mounted instrument, FIES can be used at any time, also for short periods of time while other instruments are mounted.

The currently installed fiber bundle contains a high-res 1.3 arcsec fibre offering a spectral resolution of R=67000. This bundle also provides two 1.3 arcsec fibres giving R=46000 (med-res), and a fibre with a larger entrance aperture of 2.5 arcsec but a lower spectral resolution (R=25000, low-res).

FIES offers the option of simultaneous observations of wavelength reference (Thorium-Argon) spectra, for the medium- and high-resolution modes. Simultaneous sky spectra can be obtained in medium-resolution mode, restricted to wavelengths shorter than 650nm. An exposure meter is available to predict the S/N of an ongoing exposure, allowing to optimise the exposure time. A later upgrade of FIES to full polarimetric capability is being investigated.

Questions about FIES should be directed to the instrument specialist, John Telting.

Advantages and drawbacks

The particular advantages of FIES compared to SOFIN and other high-resolution spectrographs on La Palma are:

• A high degree of mechanical and thermal stability, which allows good precision in radial-velocity determinations and accurate flat-fielding in demanding spectrophotometric work.
• The freedom to schedule observations with FIES independently of the instrumentation mounted at the main focus, and thus to follow variable objects with periods of the order of weeks without blocking the telescope for other programmes in the meantime.

In a transition period, programmes requiring capabilities not covered by FIES (UV coverage; NIR coverage 0.7-1.0 micron; Zeeman measurements) may still request to use SOFIN, but with limited freedom as regards scheduling.

Data reduction

FIES comes with dedicated reduction software (FIEStool), which provides a fully reduced spectrum for quick-look analysis after the end of each exposure, using library calibrations. The same software is also available to observers for final analysis of the data using the nightly calibration frames.

General documentation FIES commissioning report Images and technical drawings of FIES FIES project development pages (old docs) Staff pages (Staff only!)	Instrument specifications Instrument efficiency, count rates, PSF, fringing Spectral format (orders, dispersions) Wavelength/velocity zero-point accuracy Detector setup and readout times ,   gain/RON monitoring Exposure-time calculator ,   exposure-meter count calculator Atmospheric Dispersion Corrector (ADC) More detailed information
Standard stars and Data reduction Flux standards,   radial-velocity standards FIEStool info and distribution FIEStool master-frame database Thorium-Argon maps: blue atlas ,   blue atlas for dying ThAr lamp,   old red atlas	Observing guides and tools FIES Quick Reference Guide ,   NOT/FIES Observers Cookbook Sequencer command lists:   FIES,   STANCAM,   TCS Sequencer scripts:   FIES/STANCAM,   TCS Create TCS target catalogue,   INGs visibility plots,   NOT observing tools FIES for ALFOSC user,   FIES for MOSCA user,   FIES for NOTCam user