HET Technical Overview

(note: this page describes and depicts the HET before the Wide Field Upgrade)

  • 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)10 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: Fri, 29 Dec 2023 11:59:27 +0000 stevenj


    The Telescope

    Technical Overview

    Object Observability


    Non-sidereal observations



    LRS2 Summary

    LRS2 Details

    LRS2 Fiber Layout and Position Angle

    LRS2 Throughput

    LRS2 Observing details


    VIRUS - Summary

    VIRUS - Setting up on targets

    VIRUS - Misc details

    VIRUS - Throughput and sensitivity

    VIRUS - low surface brightness sensitivity

    VIRUS - Dithers, IFUs, Tiling

    VIRUS - Tiling observations

    Habitable Zone Planet Finder (HPF)

    HPF Details

    HPF Setting up on targets

    HPF Throughput and Exposure Meter

    HPF Data Reductions

    HRS-2 (in development)

    HRS-2 Summary

    HRS-2 Details

    HRS-2 configurations

    HRS-2 exposure meter

    HRS-2 Position Angle and Fiber layout

    HRS-2 Throughput

    Old Instruments

    HRS - old

    LRS - old

    MRS - old

    Program Preparation

    Web Management System