Gain Kelvins/Jansky of telescope:

• Telescope gain (K/Jy) measured using diode temperature and a set of calibrator sources of known flux.
• Do crosses (+/- 3 beamwidths) on well known calibrator fluxes to get the gain of telescope.
• plot of two crosses at 45 degrees with source deflection overplotted (.pdf)
• Use a 2-d gauss fit with coma and sidelobes included (see main beam and first sidelobe parameters for arecibo receiver systems ( C. heiles, 2000-04.ps)
• Do this for many azimuths, za's since gain changes with za.
• Fit curves to gain vs za using many calibrators. Do this for multiple frequencies.
• The diode temperature is used to transfer the flux of the calibrator sources to the flux of the unkown sources.
• Measure unknown source strength using the cals to get source strength in kelvins.
• Using the gain curves computed above:
• SourceJanskies= SourceInkelvins/(telescope gain (Kelvins/Jy))
  

SEFD: System equivalent flux density.

• Tsys/Gain: measures the gain of the telescope in units of Tsys rather than degK.
• Is independent of the cal value (since cal in Tsys and gain, they cancel)
  
• this is the quantity that determines the integration time needed (Tsys/Gain).
• It is good to measure both values:
• sefd shows when cal might be changing
• Tsys can jump (bad cable, electronic element) and gain K/Jy is still correct.