Endl’s turn with the Harlan Smith Telescope comes every four months. Last summer I joined him at McDonald Observatory while he searched for exoplanets. Endl emphasized several things: “Important aspects of an observing run are good coffee and good music.”

As we listened to his eclectic playlist and sipped exotic coffee, I quickly deduced that finding exoplanets is not easy. There are few “Eureka!” moments when an observer spots a planet and quickly confirms it. Exoplanet searches require gathering extensive data that are analyzed over time to prove or disprove the existence of a planet around another star.

The spectrograph exposures are limited to 20 minutes, not because the sensor will become saturated, but because Earth’s motion smears the spectra and makes the star’s radial velocity hard to calibrate. Because denser layers of air absorb and distort starlight, no stars are observed below about 25° altitude.

The observer controls the telescope. The desired target stars are listed in a software script that selects the next star after each spectrum is recorded. An efficient autoguider built into the spectrograph slit guides the telescope during the exposure. A light meter within the optical path counts the photons and determines when a sufficient exposure has been recorded, often terminating the exposure before the 20-minute limit. If the star is as bright as 4th magnitude, the exposure is only a minute long.

When an exposure finishes, the telescope does not automatically move to the next target. The operator must exit the control room, walk to the telescope and dome control desk, and hold down a dead man’s switch to move the telescope. This keeps eyes on the telescope to prevent possible collisions with either the pier or objects on the dome floor. The operator returns to the control room and may record as many as 30 spectra per night.