McDonald Observatory: A Banker's Eccentric Bequest

William Johnson McDonald was a banker in Paris, Texas, with no professional connection to astronomy and no apparent reason to leave his fortune to the University of Texas for the purpose of building a telescope. He did it anyway. When McDonald died in nineteen twenty-six, his relatives contested the bequest in court for years. The university held on and won. The observatory opened on May fifth, nineteen thirty-nine, in the Davis Mountains, chosen for their elevation and the darkness of their skies.

The Davis Mountains corridor has some of the darkest nights remaining in the lower forty-eight states. This was not accidental in nineteen thirty-nine, and it has required active effort to maintain since then. McDonald Observatory has been a leading advocate for dark-sky ordinances in the surrounding counties, working with municipalities and ranchers to limit light pollution in a region where the next nearest large city is several hours away. The darkness that the observatory needs for its instruments is the same darkness that every other creature in the Chihuahuan Desert relies on.

The observatory's Hobby-Eberly Telescope, completed in nineteen ninety-seven, uses a segmented-mirror design composed of ninety-one individual hexagonal mirrors working in concert. The engineering decisions made for that instrument influenced nearly every large-aperture telescope built in the decades since.

A Paris, Texas, banker with no astronomy credentials, a contested will, and a Davis Mountains site with excellent seeing conditions: sometimes the eccentric bequest turns out to be the right one.