spectra were converted into fits format images and all data reduction was performed using the IRAF software package [^4]. The spectra were then convolved with a gaussian filter of half–width $\delta = 1.2$ cm$^{-1}$. This procedure, commonly referred to as apodization, eliminates “ringing” observed in the FTS spectra due to the finite scan path of the interferometer. The resulting apodized resolution (Rayleigh criterion) was $\delta \sigma = 2.1$ cm$^{-1}$ giving a mean resolving power of $R=3000$ in the H–band. At this stage the J– and H–band spectra were separated for ease of reduction. The slope of the continuum was normalized to 1.0 using a four–segment spline fitting function. Care was taken to keep the residuals from this fit to within 1 %.

Next we corrected the spectra for telluric absorption features present in the spectra which varied with zenith angle. We attempted to construct an opacity map for the earth’s atmosphere by dividing normalized spectra obtained of the A0 star standards at different airmass. Because of the simplicity of the A0 star spectra, showing primarily hydrogen lines in absorption, it was relatively easy to monitor the degree to which this procedure was successful. In dividing two normalized spectra of the 