A new spectrometer has been built for use in the 10μm atmospheric window which is substantially more sensitive than previous instruments for observations of 10]im emission and absorption features narrower than about 0.25 cm−1. Measurements have been made of fine structure emission lines in planetary nebulae as well as in galactic and extragalactic H II regions. The spectrometer consists of a liquid Helium cooled grating with a resolution of 1–4 cm−1 and a liquid Nitrogen cooled Fabry-Perot spectrometer which is scanned across the grating bandpass, resulting in a resolution of 0.1 − 0.2 cm−1. The system NEP is about , resulting in a minimum detectable line flux of about 10−19 w/cm2, with a 6″ aperture on the Lick 3m telescope.