The opacity of the sky is usually determined by skydip measurements. However, as of now, all official BoA releases underestimate the opacity resulting from the skydip reduction. The most likely reason for this is the assumption that the sky temperature equals the ambient temperature. This assumption overestimates the sky temperature and therefore underestimates the opacity. All opacities estimated by BoA are too low by a factor of about 1.3. For a more reliable opacity estimate, one has to combine the skydips, the taumeter measurements, and the calibrator fluxes.LABOCA sky opacities search interface.
Absolute calibration scale
The raw data coming from LABOCA just have the detector voltage output as intensity. In order to obtain the intensity in astronomical units, the data have to be multiplied with a conversion factor. This conversion factor depends on the LABOCA bias voltage, which - after several tests - was fixed to 400mV. For this bias the conversion factor is:f = 6.3±0.5 Jy/μVThis factor has been determined on the primary calibrators Mars, Uranus and Neptune during the commissioning period.
LABOCA calibratorsLABOCA primary and secondary calibration factors search interface.
Values in the table below based on the file $BOA_HOME_LABOCA/secondary-fluxes.py, dated 2009-08-23. Could not connnect to the database:
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