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Kitt Peak National Observatory

KPNO 4 Meter Mayall - Basic Parameters and Facts

This page describes the current 4 Meter configuration

  • Design concepts for very wide field Prime Focus and Cassegrain configurations
  • Additional facts relevant to possible use of the 4 Meter for large science programs

  • Location: Longitude: 111:35:59.6 W,   Latitude: 31:57:50.5 N,   Altitude: 2123.2 m MSL

    Basic Optical Data

    Primary Mirror
    Radius of curvature 21318.0 mm concave
    Conic constant -1.09763
    Mirror diameter 4011.6 mm (Drawing 2106-E1)
    Bare mirror clear aperture diam 4002.6 mm
    Central hole diam 1324 mm
    Used clear aperture diam 3797 mm (Measured by Phil Massey)
    Central obscuration diam 1651 mm (PF cage)
    Central obscuration diam 1800 mm (DESI cage)
    Light-collecting area 9.182 m²
    Light-collecting area 8.658 m² (DESI)
    PF Mosaic Focus Calibration 1.043 microns/unit
    F/7.8 Secondary Mirror
    Distance from primary 7492.0 mm
    Radius of curvature 9643.0 mm convex
    Conic constant -5.2951
    Clear aperture diam 1191.6 mm (CHECK)
    Secondary to RC focus 9306.2 mm
    Instrument rotator to RC focus 152.4 mm
    Effective focal length 31258.7 mm
    Focus Calibration 0.991 microns/unit
  • Download 4-m f/7.6 ZEMAX file
  • F/15 Secondary Mirror
    Distance from primary 8634.5 mm
    Radius of curvature 5000.2 mm convex
    Conic constant -3.09014
    Clear aperture 742.7 mm
    Secondary to SQIID focus 10895 mm
    Instrument rotator to SQIID focus 598.7 mm
    Effective focal length 57160.3 mm
  • Download 4-m f/15 ZEMAX file
  • Prime Focus (f/3.1) Corrector and ADC Prisms

    Opto-Mechanical Assembly - 4 Meter Prime Focus Corrector
    The 4-m prime focus corrector is described in Jacoby, Liang, Vaughnn, Reed, and Armandroff (1988 SPIE, 3355, 721).

    Slew Time

    Calculated slew and servo settling time for the 4-meter telescope with the new Mayall Active Primary Support (MAPS) implementation. Slew motion occurs in both HA and DEC simultaneously, so the time estimate should use the longer of the two motions.

    South East Annex Position

    The position of the telescope when at the South East Annex is:
    Hour Angle = 3:44:40 E. and Declination = 31:36:00 S.

    4MAPS - 4 Meter Active Primary System

    4MAPS Manual (NOAO only)

    Risley Prisms - Cass Focus

    Risley Prisms Deployable
    Clear Aperture 172 mm
    Total Thickness 104 mm
    Front Element to R-C Focus 931 mm
    Clear Field f/7.8 45.3 mm = 298 arcsec


    Cassegrain Cage Mechanical Data
    * datum=back of primary mirror cell
    ComponentWeight(lb)Moment (in-lb)*
    Instrument rotator 960 6720
    Guider 640 11520
    Allowable instrument 1350  
    Total load 2950 72570
    additional weight information

    Optical Layout FigureAutomatic Guider Bolt Pattern
    Cassegrain Cage ClearancesCassegrain Instrument Rotator
    Cassegrain Guider Assembly 


    There are some old (and old-fashioned paper) enormous drawings of the dome and environment, but they are like ancient papyrus and very crowded with information.

    Building Information

    Mayall HA Operation Limits

    DeclinationLower Shutter Up
    Airmass = 2.1*
    Lower Shutter Down
    Airmass = 3.0

    * Note: The Airmass=2.1 limit was determined for Mosaic3. For DESI, with its 1.5 degree field, it's advised to point only to targets of airmass < 2.0 with the lower shutter raised.

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