New Q-wide order-sorting filter
- 1R4 is the filter installed and its transmission spectrum was only measured at room temperature (295K).
- 276 is the sample filter produced in the same batch as 1R4.
- 1R4 @ 16K was calculated from (1R4@295K)/(276@295K)*(276@16K).
- 276 @ 16K was actually measured.
- Peak transmission for 1R4@16K is approx. 75.57% @ 20.26 μm.
- FWHM is approx. 12.97 μm (from 16.00 to 28.97 μm) but see below.
New Q-wide vs. sky
As can be seen in the plot above, the short wavelength cut-off is probably defined by the atmospheric transmission (becomes reasonable > 17 μm?), and the long wavelength cut-off is likely to be set by the combined effect of the KBr entrance window and the Si:As detector quantum efficiency (both falling rapidly beyond ~26 μm?).
New Q-wide vs. old Q-short
As the new Q-wide filter is on average about 10% more transparent than the old Q-short filter (scanned thin black line), it is expected that the sensitivity of the new QM mode would perhaps be slightly more sensitive than the old QM-short mode.