Hobby-Eberly Telescope

The HET was designed and constructed with a unique objective: to gather a very large amount of light, specifically for spectroscopy, at extremely low cost.

A fixed elevation-axis design, based on the radio telescope at Arecibo, and an innovative system for tracking stars, contributed to an 80% reduction in initial costs compared to optical telescopes of similar size. The primary mirror of the HET is the largest yet constructed, at 11.1 x 9.8 meters. At any given time during observations, only a portion of the mirror is utilized. The HET's 9.2 meter effective aperture makes it currently the world's fourth largest optical telescope.

Work is underway to modify the telescope for the upcoming Dark Energy Experiment. A new tracker, the massive framework on the top of the HET, will increase the telescope's field of view. The addition of 150 integral field spectrographs, mounted to the sides of the main framework, will give the HET the ability to map the expansion rate of the early universe, looking back in time billions of years, to measure how clusters of galaxies moved in relation to one another as the universe evolved.

Wide Field Upgrade

The Wide Field Upgrade (WFU) is the first phase of the HETDEX retrofit. Keep up with progress at HET Blog, a forum where users can post articles, comments and photos of the work. Time-lapse movies and live webcams are available at HETDEX WFU.

hobby-eberly telescope


HET Observing Support


Night Reports


The pages of Mt. Fowlkes engineering staff, including policies and procedures, operations schedules, the problem report management system, and other information.

HET Engineering

Trimester Reports

The Trimester reports are prepared by the HET Lead RA and include information about the seeing, weather, allocation of observations by partner, distribution of objects and status of the equipment.

Science and Technical Publications

Bibliographic lists of HET science and technical publications.

We're Hiring

Telescope Operator
Electrical Engineer

Construction Photos



Mt. Fowlkes

Lat: 30° 40' 53.2" N
Long: 104° 00' 53.0" W
Elev: 2025 m above geoid


HET Partners

University of Texas at Austin

Pennsylvania State University

Ludwig Maximilians Universität

Georg August Universität

het logo
hetdex framework


Hobby-Eberly Telescope Dark Energy Experiment

HETDEX: Illuminating the Darkness