Updated Throughput Plot

With some help from Kristin and Curtis I have made some changes to the throughput plot Kristin posted in December 2013.  In the plot below, I use her data, scaled for the factor of ~2.8 difference between the a-omega value used in the previous plot and the telescope-design value, which I believe is closer to the effective acceptance angle based on Bob's earlier post.

Besides that change, I've eliminated throughput values for each filter that fall below 60% of the highest throughput value calculated for that filter.  The lower values tend to be for angles far off the blaze in weaker orders.  My original method was to limit results to echelle angles +/- 10 degrees from the blaze, but I haven't been able to locate all the data needed for that approach so that will have to wait for later.

I've omitted the filter labels and color variations in the data point for clarity, but these can be added back as desired.  I hope to use this plot or something like it in the commissioning report slide deck.

Throughput calculations

Bob McMurray posting from Mark's account.

The throughput calculations performed by the IDL journal file for the various filters appears to have an error in calculating the A-omega value. The easiest way to see it is looking back up from the pixel area, where the A is a 25 micron square and the omega is the internal f10 beam. The file uses the pixel area and the externally measured angle, which is variously F18 or F16.66 or something in that range. If you use the f10 value here, and assume your FOV is filled by the blackbody, you can take the emissivity of the BB per cm^2-sr and just multiply by the conserved A-omega to get flux in photons/sec-Hz from the BB formula. This gives a factor of 3-4 more light entering the instrument, and therefore a throughput (detected electrons/photon) that is 3-4 times smaller than had been calculated. I think these numbers are in line with what we expect from the various efficiencies of the optics.