Updated NSFCam Sensitivity (March 1998)

Below are the results of recent measurements (March 16, 1998) of
background count rates and the sensitivity of NSFCam through various
broad-band filters. Note that, except for H, the sensitivities are
0.1 to 0.4 magnitudes lower (less sensitive) than the values quoted
in the January 1996 version of the NSFCam User's Guide.

  Background = background count rate in electrons per square
      arcsecond per second (with a gain of 10 electrons/ADU).
  3-sigma Magnitude is for a total integration time of 1 minute
      on source and 1 minute on sky and assumes 2" x 2" images.

 Filter  Background [magnitude/sq arcsec]    3-sigma Mag.
 ------  --------------------------------    ---------------
  J       6.1 x 10(3)  [ 15.4 ]               20.2
  H       1.7 x 10(4)  [ 14.0 ]               19.2
  K       1.8 x 10(4)  [ 13.3 ]               18.5
  L       1.4 x 10(7)  [  5.1 ]               13.9
  L'      2.4 x 10(7)  [  4.3 ]               13.4
  nbM     9.5 x 10(7)  [  0.7 ]               10.5

Assuming background-limited performance, signal-to-noise ratio
scales directly with the source flux and with the square root of
the total integration time.


--Peter Bryant
  bryant@irtf.ifa.hawaii.edu