Yet another factor to keep in mind in assessing EXES performance is the precision of placement of the IRTF focus (by changing telescope primary-secondary spacing) and the effect of this placement on spot size at the EXES detector.The attached image shows the progression of detector spot sizes (on-axis, in high-res mode, at 7μm wavelength) as you change the IRTF telescope spacing over a 2mm range.
At the 'design' spacing, spot size is close to diffraction limited.
Plus and minus 1mm from design spacing of the IRTF mirror, spot size is ten times the diffraction limit.
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