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Calibration at the HHT

The sky is clear, the telescope is moving towards your favorite sources, and you have your receiver(s) tuned and ready to go! The question of calibration has arisen. However, it is not a trivial issue, particularly at shorter wavelengths, where the sky opacity is very important. While the HHT staff will try to provide you with the best available numbers for the expected receiver characteristics, you ultimately have to make sure that you have the data you need to turn your source observations into the beautiful paper you promised your TAC. Therefore, we advise first-time users of the HHT (and even our experienced observers who might have been dallying in other wavelength regimes recently) to review some or all of the calibration papers listed below. In addition, the observer is encouraged to look at the HHT observer's manual chapter(s) on calibration.

  1. Useful Background Papers

    For reference, we list a number of papers which discuss the calibration of millimeter data. Where possible, we include a link to a postscript copy of the paper. We urge that the potential observer look these papers over before he/she visits the telescope for the first time.

  2. SMTO 230 GHz Radiometer and Weather

    We have a little tau meter that updates every half hour typically and provides an estimate of the 225 GHz opacity. In general, taus(225 GHz) of lower than 0.06 indicate good submillimeter observing conditions. taus between 0.06 and 0.10 are good for observations around 460-490 GHz, and up to 0.20 or so for 230 GHz observations.

  3. Example Transmission Plots for Various Taus(225 GHz) at the HHT

    We have calculated some example transmission plots for different taus(225 GHz). The transmission plots are displayed over the frequency range 200 GHz to 960 Ghz. They have been calculated explicitly for the HHT site.

  4. Calibration Terms UNDER CONSTRUCTION

    We present some of the basic calibration terms used in the background papers and in the SMTO observer's manual.

Inexperienced submillimeter observers must discuss what calibration observations will be necessary for their program with their contact person at the HHT or any Friend of the Telescope.

Last Changed: September 16, 1997 by Harold M. Butner