Primary and secondary calibrator observations have been reduced using the specifically designed
dimmconfig_bright_compact.lis. The maps produced from this are then analysed using tailor-made
Picard recipes. For instructions on applying the FCFs to your map see Section 8.1.
A map reduced by the map-maker has units of pW. To calibrate the data into units of janskys (Jy), a set of bright, point-source objects with well-known flux densities are observed regularly to provide a flux conversion factor (FCF). The data (in pW) can be multiplied by this FCF to obtain a calibrated map. The FCF can also be used to assess the relative performance of the instrument from night to night. The noise equivalent flux density (NEFD) is a measure of the instrument sensitivity, and while not discussed here, is also produced by the Picard recipe shown here. For calibration of primary and secondary calibrators, the FCFs and NEFDs have been calculated as follows:
SCUBA2_FCFNEFDtakes the reduced map, crops it, and runs background removal. Surface-fitting parameters are changeable in the Picard parameter file.
FLUX_450.MYSRC = 0.050and
FLUX_850.MYSRC = 0.005(where the values are in Jy), for example.
The measured peak signal here is derived from the Gaussian fit of beamfit. The peak value is susceptible to pointing and focus errors, and we have found this number to be somewhat unreliable, particularly at 450m.
Analysis of the SCUBA-2 secondary calibrators has allowed calculation of the transmission relationships for the SCUBA-2 450 m and 850 m pass-bands to be determined. Full details of the analysis and on-sky calibration methods of SCUBA-2 can be found in Dempsey et al. (2013) .
Archibald et al. (2002)  describes how the Caltech Submillimeter Observatory (CSO) 225 GHz opacity, , relates to SCUBA opacity terms in each band, and . The JCMT water-vapour radiometer (WVM) uses the 183 GHz water line to calculate the precipitable water vapour (PWV) along the line-of-sight of the telescope. This PWV is then input into an atmospheric model to calculate the zenith opacity at 225 GHz (). This allows ease of comparison with the adjacent CSO 225 GHz tipping radiometer. The opacities have been as:
The SCUBA-2 filter characteristics are described in detail on the JCMT website1.
The extinction correction parameters that scale from
to the relevant filter have been added to the map-maker code. You can override these values by
ext.taurelation.filtname in your map-maker config files to the two coefficients
that you want to use (where
filtname is the name of the filter). The defaults are listed in