The files used for these calculations have a smaller grid of values than those for the mid-infrared atmospheric transmission page which covers 5 to 30 microns. However the resolution used here is higher than for the mid-IR grid. Water column values of 0.5, 2.5, 4.5, and 6.5 PMM were used for the calculations. Airmass values of 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0 were used in the calculations. The program interpolates for values that do not match the grid. The interpolation is relatively simple so one should not over-interpret such spectra from this page.
If you wish to see the directly observed atmospheric transmission (for Kitt Peak, not for Mauna Kea) try the Arcturus spectrum page.
The number of values returned is independent of the resolution, and reflects the wavelength sampling of the originial ATRAN models. When lower resolutions are requested the values are convolved with a gaussian of the appropriate width. In fact the wavelength resolution requested in microns (or the value calculated from the resolution given as wavelength/sampling interval) is assumed to be the sigma value for the gaussian function used in the convolution. Thus the line FWHM from the convolution will be about 2.35 times the wavelength resolution specified.
This page was last modified March 30, 2006.Kevin Volk (firstname.lastname@example.org)