8 July 2014 Better flat-fielding for ground-based UV spectrographs
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A new technological development, the laser driven light source (LDLS), in which a laser excited plasma emits intense continuum radiation over a wide wavelength range from well below the atmospheric cut-off up to 800 nm, promises to greatly improve our ability to provide high quality flat-fields for astronomical spectrographs. Its particular strength lies in the ground-based ultraviolet (UV). We report on tests conducted with a LDLS using FORS2, UVES, X-Shooter and CRIRES at ESO’s Very Large Telescope (VLT) in August 2013. Comparison with standard calibration sources such as halogen and deuterium lamps shows that with the LDLS flat-fields with a better balanced dynamic range and excellent signal to noise ratio can be achieved within short exposure times. This will enable higher quality science at the short wavelength end of existing spectrographs at the VLT. Furthermore the LDLS provides exceptional stability and long lifetime as important operational aspects. Optimised UV spectrographs such as the proposed CUBES (wavelength range 300-400 nm) project will be able to take full advantage of this development removing the long-standing limitation of signal to noise ratios of UV flat-fields.
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Florian Kerber, Florian Kerber, Reinhard Hanuschik, Reinhard Hanuschik, Sabine Moehler, Sabine Moehler, Alain Smette, Alain Smette, Jonathan Smoker, Jonathan Smoker, Pierre Bourget, Pierre Bourget, Peter J. Dwyer, Peter J. Dwyer, Michael Rotschädl, Michael Rotschädl, "Better flat-fielding for ground-based UV spectrographs", Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 914743 (8 July 2014); doi: 10.1117/12.2055179; https://doi.org/10.1117/12.2055179

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