The Line Of Sight Sky Absorbtion Monitor (LOSSAM)
|    Variability     Local Humidity     Thin Cirrus|
Example of two consecutive nights of similar average extinction
(0.12 magnitude per airmass) but of
different variability (6Feb00:rms=0.008m, 7Feb00:rms=0.013m):
both were declared photometric by the observers. In the night of 7 February (below),
the sharp decrease of the extinction coefficient at about 1h45 is coincident with the
abrupt change in air temperature, indicating a change of wind flow pattern in the first km
above the site.
Example of a clear night which shows a change of extinction correlated with the local humidity: this night is not photometric according to LOSSAM criteria.