Subject: APO + DSC efficiency

From: Krzysztof Stanek

Submitted: Thu, 22 Feb 1996 17:20:39 -0500

Message number: 22 (previous: 21, next: 23 up: Index)

I have just performed efficiency calculations for the 3.5-meter+DSC 
system. It seems the efficiency is low, about 14% in Harris V.
This means we loose about
1.5 - 2 mag, making the telescope effectively an 1.5 - 2-meter telescope.
Details below and on request.

Kris Stanek
Princeton University Observatory

------------------------------------------------------------------------------

      Efficiency calculations using standard field RU152 (Landolt 1992)


 Name     x        y      m_v1    DU_v1      mv_2    DU_v2     m_V      Flux
------------------------------------------------------------------------------
RU152A  795.26   423.23  12.534  96875.36   12.467  103071.5  14.341   1841090 
RU152C  905.74   577.84  10.403  689930.    10.339  731887.1  12.222  12855100 
RU152B  728.97   512.77  13.166  54143.23   13.127  56142.75  15.019    993290 
RU152E  463.72   606.38  10.566  593898.    10.513  623643.9  12.362  11404480 
RU152F  436.79   744.92  12.736  80458.02   12.675  85115.3   14.564   1503400 

DU_v1: flux at airmass 1.62  [DU]
DU_v2: flux at airmass 1.22  [DU]
Flux: expected flux at airmass 1.22 [photons] (based on number of photons
                               in V from Vega I got from Mike Richmond)
m_v1,m_v2: used only to derive atmospheric extinction coefficient

Atmospheric extinction: 0.14/(unit airmass)  [mag]

Efficiency: <Flux/DU_v2> = 0.055

If gain=2.5 e-/DN, efficiency is about 14 %
Variations of the noise level of the sky flats are in agreement with the
gain of = 2.5 e-/DN.
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