Shown below are the photon transfer results from the flat-field data taken by Leonid for C2, Fowler=1.  The gain and read noise are consistent with the laboratory results.

Shown below are the results from the sky images taken by Leonid.  The data set consist of 2 integrations at varying exposure times and fowler sampling.  The total noise is calculated by the standard deviation of a relatively starless piece of sky.  These values are plotted with the solid lines.  Using this measured value for the read noise at fowler=1 (above), we can approximate the read noise for fowler=N using the equation RN/sqrt(N).  (Ultimately, we’ll have measurements of the read noise at all fowler sampling.)  The background noise (noise_bg) can then be calculated from the following equation:

Total Noise = SQRT(RN^2 + noise_bg^2), where noise_bg = SQRT(flux_bg*t_int)

The background noise is over-plotted with a solid horizontal line for each integration time.

It depends what we define “background limited” to mean.  If we define this to mean noise_bg > 1 * RN, the 60second integrations are background limited in both Z and Y bands for Fowler =1 (and for even shorter integrations in Y-band).  The shorter integrations become background limited for Fowler > 1.