XSHOOTER Overview

Publications based on data obtained with XSHOOTER should quote the following reference paper:

Vernet et al. 2011, A&A, 536A, 105 .

XSHOOTER in a nutshell

  • The XSHOOTER science case document is available here.
  • XSHOOTER is a multi wavelength (300-2500nm) medium resolution spectrograph mounted at the UT2 Cassegrain focus until end of P91. Starting from P92, XSHOOTER will be moved to UT3. Its location for P93 and above is not yet decided.
  • XSHOOTER consists of 4 arms with the Acquisition and Guiding camera. It has 3 spectroscopic arms, each with optimized optics, dispersive elements and detectors:
    • UVB, covering the wavelength range 300-559.5 nm
    • VIS, covering the wavelength range 559.5-1024 nm
    • NIR, covering the wavelength range 1024-2480 nm
  • Each arm is an independent cross dispersed echelle spectrograph completed with its own shutter and/or slit mask. The incoming light is split into the three different spectrographs/arms through 2 dichroics (cut off wavelengths 559.5 nm and 1024 nm for the separation of the UVB-VIS light and VIS-NIR light, respectively). For each arm the spectral format is fixed. The orders in each detector are highly curved and the sky/arc lines within each order are highlytilted.
  • Three piezo controlled mirrors, located in front of each arm, guarantee that the optical path is maintained aligned against instrument flexure and correct for differential atmospheric refraction between the telescope guiding wavelength and each arm central wavelength.
  • Two pairs of ADC (Atmospheric Dispersion Corrector) prisms in the optical path of the UVB and VIS arm compensate for the atmospheric dispersion at different airmasses. No ADC is mounted in front of the NIR arm.
  • The Acquisition and Guiding system (A&G) consists of a1.5'x1.5' FoV technical CCD for the target acquisition. A filter wheel equipped with the Johnson and SDSS filters can be used for the acquisitions. There is not secondary guiding in XSHOOTER.
  • The five positions slide, located before the UVB, VIS and NIRspectrograph, allows to insert an image slicer in the optical path and perform IFU spectroscopy of a 1.8''x4'' FoV. IFU mode observations are an alternative to slit mode observations.
  • An internal calibration unit, equipped with pen-ray (Ar, He, Neand Xe), Th-Ar, Halogen and D2 lamps, is used to produce the necessary calibration frames (flats, arcs, oder definition, format check and 2Dmap frames).
  • The figure below shows the schematic overview of the instrument.

    XSH