Commissioning of a continuously tunable frequency comb for wavelength and line-spread-function calibration
Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
Final Report Abstract
On-sky tests with a versatile and compact astro-comb suitable for medium and low-resolution spectrographs were reported. The astro-comb provides 300 narrow lines which are tracked with a wavemeter with 0.3 pm accuracy. With this accuracy we measured an offset between wavemeter and Neon-calibrated results. While its origin could not be exactly determined, possible explanations couldbe linked to small optical path differences within the spectrograph as well as errors in refering wavelengths neither to vacuum nor to the Calar Alto air but to a sea-level standard air. Nevertheless, we successfully wavelength calibrate stellar objects (HD3765 and HD219538) as well as bright OH emission lines from the sky. In summary, it was shown that this astro-comb could be transported from the laboratory to be used for real night-time observations at a telescope. The astro-comb was proven to provide an alternative calibration source to the classical spectral line lamps used for astronomical spectrographs. Finally, our tunable astro-comb technique might find applications to accurately determine the line spread function of spectrographs at any resolution.
