Throughput and Background Brightness
The table below contains the
most recent determinations of the INGRID/NAOMI
zero points (zp
). These are
the magnitudes, in each band, that give
1 ADU/s. Note that the zeropoints can change
from time to time, mainly due to cleanness of the telescope and NAOMI's
+ 2.5 log (F
) + kx
, where m
is the star's magnitude, F
is the flux in ADU/s, k
is the extinction constant and x
is the airmass.
Ranges of typical values of background brightness are
given in columns 2 and 3, in mag/sqr-arcsec and ADU/s respectively. The
background brightness in J and H is dominated by
airglow emission and
can vary considerably from night to night, and also during the same
night. Changes up to ~150% of the values shown here are not unlikely.
The K/Ks backgrounds are dominated by
The exposure time before saturation (obtained from the values in
column 3) is given in the last column of the table.
(mag per 1 ADU/s)
|Time to saturation *
||~ 6.5-16.5 hours
||~ 1-3 hours
||~ 3.7 mins
* Time to reach the full well limit (28000 ADU).