The Hobby-Eberly Telescope at the McDonald Observatory is primarily used for spectography. Its mirror consists of 91 hexagonal elements for a total area of 11m x 10m. When combined with the fibre optic coupled high resolution spectrograph, it can measure stellar radial velocities with resolutions down to 1m/s.

The main task of the Hobby-Eberly Telescope is finding extra-solar planets by looking at the radial-velocity variations of stars.