To obtain high resolution spectroscopy (R = 1000, 2200) in the K-band, two Fabry-Perot etalons can be mounted in front of the camera. Their finesse and the resolution for different wavelengths are tabulated in table 2.7 and 2.8.
Table 2.7: Finesse and resolution for the
low resolution Fabry-Perot etalon
Table 2.8: Finesse and resolution for the
high resolution Fabry-Perot etalon
The transmission in the wavelength range from 1.9 to 2.4 
is 85 % for the low resolution etalon and 65 % for the high
resolution etalon.
Figures 2.4 and 2.5 show the shift in passband
across the field of view. Within the the recommended pixel-scale
of 
(dashed lines), this shift is less than
0.2 nm for the low resolution etalon and less than 0.5 nm for the
high resolution etalon.
Figure 2.4: Shift in passband for the low resolution
Fabry-Perot etalon. The dashed lines represent the field of view
in the scale. The the short, perpendicular tick marks
point "downhill". North is right and east is down
Figure 2.5: Shift in passband for the low resolution
Fabry-Perot etalon. The dashed lines represent the field of view
in the scale. The the short, perpendicular tick marks
point "downhill". North is right and east is down