HET Technical Overview

  • Primary Mirror
  • The primary mirror is composed of 91 segments, each hexagonal in shape and 1 meter across. They form a large spherical surface having a radius of curvature of 26.164 meters. Each segment is positioned under computer control to yield a hexagonal primary mirror 11 meters in diameter with an area of 77.6 square meters.
    Primary Mirror Array
    Maximum Diameter11 meters
    Area 77.6 square meters
    Focal Length 13.08 meters
    Filling Factor ~96.6%

  • Telescope Structure
  • The mirror resides within an overall telescope structure that is made of welded steel and weighs 60 tons. It rotates on air bearings around the complete 360° horizon. It is fixed in zenith angle at 35° which along with the azimuth rotation allows it to access declinations from -10°20' to 71°40' (about 70% of the celestial sky from this latitude, but 81% of the scientifically useful airmass range < 2.5).

  • Tracking
  • The HET is a tilted optical Arecibo type telescope, which means that tracking of astronomical targets is achieved through moving a tracker optical package, which contains spherical aberration correction optics and instrument feeds, rather than the whole telescope. Tracking time across the 12° focal surface ranges from 0.75 hr. at the equator to 2.5 hr. at the north declination limit.

    Telescope Parameters
    Telescope Tilt Angle 35°
    Angular Range (FoV tracker)12°
    Declination Range -10°20' to 71°40'
    Site Altitude ~2 km (6640 ft.)
    Tracker Optical Package
    Maximum Diameter 490 mm
    Type Four Element Gregorian
    Effective F. Ratio (output) 4.7
    Focal Plane FoV 3.5 arcminutes diameter
    Final Image Scale 5 arcseconds/mm
    Entrance Pupil Diameter (on primary)9.21 meters

  • Enclosure and Facility
  • The HET is located at:
    W 104 00 53.0
    N 30 40 53.2
    2026 meters above the geoid
    on the WGS84 system

    The HET is housed in a spherical dome 85 feet in diameter and standing 100 feet above the ground. A 2500 square-foot building houses maintenance and service equipment and the telescope control room. A 90 foot tower contains an interferometer at the primary mirror center of curvature which is used to align all the segments in piston, tip and tilt.

    Last updated: Thu, 03 Mar 2011 11:36:32 -0600 caldwell


    The Telescope

    Technical Overview

    Object Observability




    HRS Instrument Summary

    HRS - Details

    HRS Configurations

    HRS Throughput

    HRS Wavelength Calibration


    MRS Instrument Summary

    MRS Configurations

    MRS Throughput

    MRS Wavelength Calibration


    LRS Instrument Summary

    LRS Configurations

    Multi-object Unit

    LRS Throughput

    LRS Spectral Resolution

    LRS Wavelength Calibration

    Visitor Filter Information

    LRS Position Angles

    Blind Offsetting

    Guide Stars Limits

    LRS Update from Gary Hill

    Program Preparation

    Web Management System

    Other HET Documentation