Mount Lemmon Observing Facility

The Mount Lemmon Observing Facility (MLOF), built in 1970 near Tucson, AZ, was established following the success of the O'Brien Observatory in Minnesota, to build a larger, infrared-optimized telescope at a dry, high-altitude site. Under the leadership of Bob Gehrz, various locations were surveyed before Mount Lemmon was chosen for its proximity to University of Arizona facilities. MLOF houses a 60-inch, f/15, infrared-optimized Dahl-Kirkham Cassegrain telescope, which operated manually for its first 19 years until Gehrz and Terry J. Jones modified it in 1989 for fully automated, remote-controlled operation via phone modem.

With the recent advent of optical sky surveys identifying transients across the Universe every night, the need for telescopes capable of rapid response has grown urgent. To meet this demand, members of MIfA, in collaboration with Richard (Dick) Treffers of Starman Systems, have further automated MLOF’s observing system to enable remote—and eventually robotic—operations. To take advantage of this new observing capability, MIfA personnel are constructing a joint optical and near-infrared imager, whose sensitive follow-up capabilities will be used to characterize transients found by these surveys.

CURRENT STATUS

MIfA faculty Pat Kelly and Bob Gehrz have led an effort to install a new telescope control system and instrumentation in order to enable rapid response, automated observations. Kelly, Gehrz, and Michael Coughlin plan to use the upgraded facility to follow up transients from ongoing and planned large-area surveys. The effort, carried out together with Dick Treffers, has involved the installation of a parallel telescope control system, weather station, mirror-cover opener, and weatherization of the dome.

The upgrade has also included the fabrication of a “transfer box” that directs light from the telescope to one of four potential instruments within seconds using a set of sliding mirrors. A pair of optical and near-infrared imagers will be deployed in conjunction with the transfer box first during the spring and summer of 2025.

Design, funded in part by the Research & Innovation Office at UMN, is also underway to develop an always-mounted instrument that can simultaneously acquire imaging in six UV-through-near-infrared wideband filters. The instrument will also have the ability to acquire optical and near-infrared spectroscopy. Moreover, the new optics will also substantially correct the off-axis aberrations inherent to the Dall-Kirkham optical design, and thereby enable much wider-field observations.

Early Observations and Discoveries at MLOF

The first large-scale census of the infrared radiation from RV Tauri stars and other evolved Post Main Sequence (PMS) stars
- Gehrz, 1971. Infrared Radiation from RV Tauri Stars.
- Gehrz, 1972. Infrared Radiation from RV Tauri Stars I. an Infrared Survey of RV Tauri Stars and Related Objects.
The first comprehensive survey of the SEDs of pre-Main Sequence stars (Cohen 1973 a, b, c, and d)
- Cohen, 1973. Infra-red observations of young stars I. Stars in young clusters.
- Cohen, 1973. Infra-red observations of young stars II. T Tau stars and the ORI population.
- Cohen, 1973. Infrared observations of young stars III. Nebulous emission-line stars.
- Cohen, 1973. Infrared observations of young stars IV. Radiative mechanisms and interpretations.
The first attempts to obtain systematic 7-14 μm CVFW spectroscopy of stellar sequences
- Merrill and Stein, 1976. 2-14 µm stellar spectrophotometry I. Stars of the conventional spectral sequence.
- Merrill and Stein, 1976. 2-14 µm stellar spectrophotometry II. Stars from the 2 MU M infrared sky survey.
- Merrill and Stein, 1976. 2-14 µm stellar spectrophotometry III. AFCRL sky survey objects.
The first attempt to detect the 10 μm radiation from globular cluster cores
- Cohen and Fawley, 1974. Ten micron observations of globular clusters.