T-ReCS contains 7 slit masks for spectroscopy, plus an "open" mask and an occulting bar for imaging mode. The slit widths are chosen to match the lambda/D and 2*lambda/D conditions at the upper end of the 10 and 20 µm wavelength bands, plus the lambda/D condition at three additional wavelengths in the 10 µm band. The lambda/D slits will generally provide the best spectral resolution in good seeing; the 2*lambda/D slits may be better in poor seeing or for fainter sources. The length of each slit and the occulting bar is 21.6" which spans the 240-pixel vertical height of the array (position angle = 0 degrees). Slits and occulting bar angles can be changed by specifying the angle required as the instrument position angle.

^a HR = high resolution; LR = low resolution