The 2.4-m Hiltner telescope optics are very close to a Ritchey-Chretien design with access to both f/7.5 and f/13.5 Cassegrain foci. There is no prime focus (except for engineering tests).
NOTE: at the present time (1998), the f/13.5 focus is not available.
At f/7.5 the image scale is 11.528 arcseconds/mm; at f/13.5 the scale is 6.399 arcseconds/mm.
One can not change between f7.5 and f/13.5 during the night, as it requires a top end change. This requires 2-3 hours during a week day.
All mirrors are made of low expansion Cer-Vit, with aluminum coating.
The optical surface of the primary is 0.96 wave peak-valley, and 0.07 wave rms. The primary mirror has a slight turned-down edge and has been masked (by painting) to a clear aperture of 2.32-m yielding an f/2.07 beam.
The precise position of the telescope is longitude = -111.6167 degrees and latitude = 31.950 degrees. The altitude is 1938.5 meters.
The distance from the zenith to the back dome bulkhead (where the shutter motor resides) is only 1.05 meters. As a result the dome occults when the telescope is pointing within 1.25 degrees of the zenith. A maximum of 1.9% of the light can be lost by this vignetting, which is tabulated as a function of telescope position in the telescope manual.
A complete operations manual (from which all of this information was extracted) is kept in the control room.