Astronomical Calibration Lamps
Astronomical Calibration Lamps are the preferred wavelength calibration solution for most astrophysical spectrographs. In the era of extremely large telescopes, it is often the accuracy of the calibration source that limits the achievable precision. Astronomical spectrographs require precise wavelength calibration sources and a detailed understanding of the associated uncertainties and systematics. Below 900 nm, Thorium-Argon (Th/Ar) hollow cathode lamps are the generally applicable source of standards for wavelength calibration in the near IR. Th/Ar gives a very rich emission line spectrum over a wide wavelength range and is thus very useful for high dispersion work with the ease and efficiency of operation of a commercial discharge lamp.
Continual improvements in the line list have now enabled Th lamps to be used to calibrate almost the entire optical bandpass with high precision. Thorium (232Th), an element often used as the cathode for such lamps, exhibits many of the desired characteristics of an atomic emission calibration source. Other gas fillers elements such as Uranium can also be used as a calibration source.
Th/Ar part number P858A