Imaging: Sensitivity Tables

The UIST 0.12"/pix and 0.06"/pix camera modules have similar sensitivities. These values assume background limited performance - at very short exposures signal-to-noise does not scale with square root of time for a given signal, as there is some extraneous noise seen in the instrument. See notes below on other filters and overheads.  

With narrow-band filters for continuum sources the source signal and background signal are both reduced by the reduced passband of the filter, i.e. by about a factor of 10. The Signal-to-Noise ratio for a continuum source will therefore decrease by the square-root of the ratio of filter bandpasses, sqrt{broad/narrow} ~ 3.2, and the magnitudes in the above table will decrease by 1.25. For an unresolved emission-line source, only the background signal is reduced by the reduced passband, so the Signal-to-Noise ratio for a line-emission source will increase by the square-root of the ratio of filter bandpasses, sqrt{broad/narrow} ~ 3.2, and the magnitudes in the above table will increase by 1.25.

Overheads for broadband thermal imaging can be significant. Either the 0.06 or 0.12 "/pixel cameras can be used; the smaller pixel scale is more efficient but of course gives a smaller field. The full 1024x1024 readout can be used with the 0.12"/pixel camera with the L' filter. Due to high background emission, the central region of the array goes to highly non-linear regime in M' with the 0.12"/pix camera when we do the 1024x1024 readout. Hence in M', one has to do 512x512 sub-array readouts. However, 1024x1024 readout is possible in the M' with the 0.06"/pix camera. Both 512x512 and 256x256 subarrays are available although the smallest subarray is very rarely used. Exposure times and overheads for L' and M' for each camera are given here. See also the separate page on thermal imaging.