Calibration Sources

Flux calibrators

Here is a list of the positions of regularly used System temperature calibrators:

        RA(1950)        Dec(1950)
Cas A   350.2953         58.558
Cyg A   299.43750        40.596
Tau A    82.8791         21.966
Vir A   187.074          12.668

Their flux densities are can be calculated from this table, where frequencies, `f', are given in MHz and flux densities, `S', are given in Jy:

Cas A

From 300MHz to 31GHz

log(S) = 5.745 - 0.770*log(f)

This decreases at about ( 1.87-0.3*log(f) )% per year from the year 1986.

Cyg A

From 20MHz to 2GHz

log(S) = 4.965 +0.085*log(f) - 0.178*log(f)*log(f)

and from 2GHz to 31GHz

log(S) = 7.161 -1.242*log(f)

Tau A

From 1 GHz to 35GHz

log(S) = 3.915 -0.299*log(f)

Vir A

From 400MHz to 25GHz

log(S) = 5.023 -0.856*log(f)

This gives the following antenna temperatures, for the nominal antenna gains:

Source              21cm     18cm

Cas A(in 1980)      237K     209K
Cyg A               179K     151K
Tau A               107K     102K
Vir A                24K      21K

There are also a few pointing calibrators, and their positions are given here:

        RA(1950)        Dec(1950)
3C123    68.4790         29.5720
3C218   138.9230        -11.8550

Spectral line calibrators

Here is a list of the positions of some spectral line calibrators:

                 RA(1950)   Dec(1950)     Wavelength   Comment
W3               133.950     1.064       18cm          OH masers
NML Cygnus        80.797    -1.922       18cm          OH masers 
Lockman Hole     159.242    57.333       21cm         low HI density

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