Michelle's slit mask currently contains five slits for spectroscopy as well as an "open" mask for imaging. Resolving power is inversely proportional to slit width. The width of the two-pixel wide slit (~0.4") somewhat exceeds the diffraction limit in the 10um window (1.2 lambda/D at Gemini corresponds to 0.3" at 10.0um), and is narrower than the diffraction limit in the 20um window. The three-pixel wide slit is a better match at 20um. Our best estimate of the imaging pixel scale is 0.1005 arc-seconds per pixel, based upon binary star separation measurements. In spectroscopy mode the angular size of pixels projected on the sky is twice that for imaging.