Bolocam began collecting science data in 2003 as the long-wavelength imaging
camera at the Caltech Submillimeter Observatory. The planets, along with a
handful of secondary calibrators, have been used to determine the flux
calibration for all of the data collected with Bolocam. Uranus and Neptune
stand out as the only two planets that are bright enough to be seen with high
signal-to-noise in short integrations without saturating the standard Bolocam
readout electronics. By analyzing all of the 143 GHz observations made with
Bolocam between 2003 and 2010, we find that the brightness ratio of Uranus to
Neptune is 1.027 +- 0.006, with no evidence for any variations over that
period. Including previously published results at \simeq 150 GHz, we find a
brightness ratio of 1.029 +- 0.006 with no evidence for time variability over
the period 1983-2010. Additionally, we find no evidence for time-variability in
the brightness ratio of either Uranus or Neptune to the ultracompact HII region
G34.3 or the protostellar source NGC 2071IR. Using recently published WMAP
results we constrain the absolute 143 GHz brightness of both Uranus and Neptune
to ~3%. Finally, we present ~3% absolute 143 GHz peak flux density values for
the ultracompact HII regions G34.3 and K3-50A and the protostellar source NGC
2071IR.Comment: updated based on referee's comments, published in Ap