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. APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 22 in the apo35-dsc archive. You can find APO the archive on http://astro.princeton.edu:82/apo35-dsc/INDEX.html APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-dsc@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO