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Calibration

Near-IR calibrations are discussed in detail on the general near-IR web pages, as they are generally similar for all Gemini near-IR imagers and spectrographs. A baseline calibration set (not charged to the PI) is taken for each observation, generally the minimum calibrations necessary to ensure the utility of the observations in the archive.


Note that for spectroscopic observations in the 1-2.5 µm region wavelength calibration is typically derived from the lines in the telluric absorption lines in the spectrum of the calibration star, and/or OH lines in the spectrum of the night sky. Phoenix does contain an ThAr lamp available for wavelength calibration. However, the narrow wavelength coverage of Phoenix does not always include an arc lamp line, let alone two widely spaced lines needed for an accurate wavelength scale. In the 3-5 µm region telluric lines often provide the best (and only) wavelength calibration.


In general, for spectra in the 1-2.5 µm region calibration stars should have JHK magnitudes of 5 or fainter. This is because acquisition involves imaging through the blocking filter and even short images of bright stars will result in heavy saturation of the array, the effects of which persist for up to one hour and can significantly corrupt the spectrum of a faint science target.