Observer Information
Documentation for Principal Investigators
HET blog with observing updates
Proposals instructions
Instruments, all at Prime focus (f/3.65):
Optical
| Primary Mirror, prime focus | |
| Diameter | 10.0 m (433") |
| Focal length | 36.500 m (120') |
| F-ratio | 3.65 |
| Field of view | 22 arcmin |
| Plate scale | 5.65 arcsec/mm |
| Accessible declination* | -10.3 to +71.6 deg |
| Maximum declination** | -12.0 to +74.0 deg |
| Maximum track time | 2.8 hours at Dec=+67.2deg |
*for tracks passing through primary mirror center at track center
**for tracks at least 30min long without a fully illuminated pupil at track center
Mechanical
| Primary Mirror | |
| Weight | 13.5 t (27,000 lbs) (250lb/segment) |
| Thickness | 50 mm (2 inches) at the edge |
| Material | Zerodur |
| Segments | 91 (6 spares) |
| Segment size | Hexagonal, 1m diameter |
| Shape | Spherical |
| Radius of Curvature | 26 m |
| Telescope | |
| Weight | 153 tons |
| Bearings | |
| Azimuth axis | Pressurized air bearings on concrete pier |
| Dome | |
| Diameter | 26 m (86 ft) |
| Weight | 20 t (22 tons) |
| Fixed Elevation Telescope | |
| Elevation Angle | 55 degrees |
| Angular range of tracker on sphere | 12 degrees |
Historical
| Initial Construction | |
| Started | 1994 |
| First light | Dec 1996 |
| Dedication | Oct 1997 |
| End of commissioning | Oct 1999 |
| Wide Field Upgrade | |
| HET taken offline | Sep 2013 |
| Upgrade first light | Jul 2015 |
| Early science operations | Jul 2016 |
| Full science operations | Jun 2018 |
Reference paper for the HET's Wide Field Upgrade Hill, et al 2021 AJ, 162, 298
