Zeropoint results (Nov 3, 2012 courtesy Paul Martini)

Two datasets on C26202 were obtained on 20121102, the first at airmass 1.01 (g->Y in files 145966->145970) and the second at 1.11 (g->Y in files 146108->146112). The zeropoints are consistent to better than 0.05 mag, with the exception of r-band. The average of the two zeropoints correspond to:

Filter Zpt (mag) Zpt (e-) Zpt (e-)/Expected
g 25.296 591 1.00
r 25.374 635 1.15
i 25.379 638 1.11
z 25.064 477 1.11
Y 24.154 206 1.33


Zpt (mag) is the AB magnitude that corresponds to 1 DN/s. Zpt (e-) is the number of e-/s that corresponds to AB=20 mag as assumes the gain is 4.5e-/DN. Zpt (e-)/Expected is the ratio of Zpt (e-) to the expected zeropoints calculated by Huan Lin.

Notes about the analysis:

  1. No airmass correction was applied, although this should be minimal.
  2. In all cases C26202 fell on Amp A of chip N4.
  3. The astrometric solution in the headers are off by 3.8' and 3'.
  4. While the last column indicates the performance exceed expectations, the specification is for airmass 1.3, while these data were obtained at about airmass 1.