AHO members engage in various joint activities aligned with alliance objectives: astronomical site, asset, and data preservation; collaborative public engagement and media projects; STEM-focused outreach; and strategic collaboration on mature facility operations.
There are two types of membership: “Institutional” and “Associate” (see Bylaws Article 3).
To nominate an institution for membership, please use our contact form.
Armagh Observatory & Planetarium
est. 1790
Armagh, Northern Ireland, UK
Produced the New General Catalogue (NGC)
Oldest telescope in the world in its original setting in its dome
Oldest scientific institution in Northern Ireland
Longest continuously operating observatory in the UK and Ireland
Oldest operating planetarium in the UK and Ireland
Longest continuous daily weather record in the UK and Ireland
King George III Short Telescope (0.15m, 1769)
Troughton Equatorial Refractor (0.07m, 1795)
Jones Transit Instrument (0.09m, 1827)
Jones Mural Circle (0.19m, 1831)
Grubb 15-inch Reflector (0.38m, 1835)
Grubb 10-inch Refractor (0.25m, 1885)
Calver 18.25-inch Reflector (0.46m, 1918)
Ellison “Amateur’s Telescope” (0.16m, 1920)
Michael Burton (director)
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Boyden Observatory
est. 1889
Bloemfontein, South Africa
University of the Free State
Produced the plates used by H. Leavitt to discover the P-L Law
and by A.J. Cannon for input to the Draper Catalogue
First photographic all-sky atlas
Discovery of Saturn’s moon Phoebe
First photographs of Mars
First spectroscopic binary star discovered using spectra alone
13-inch Alvan Clark telescope (0.33m refractor, 1888)
60-inch Rockefeller telescope (1.5m reflector, 1931)
10-inch Metcalf Photographic Triplet Refractor (0.25m, 1915)
1-inch Cooke lens (0.02m, 1899)
3-inch Cook Fecker lens (0.07m, 1929)
60-inch Common mirror (1.5m, 1890)
Dawid Van Jaarsveldt (curator)
Cincinnati Observatory
est. 1842
Cincinnati, OH, USA
"Birthplace of American astronomy"
Second largest telescope in the world (1845)
First public observatory in the United States
Minor Planet Center Headquarters (1947-1978)
Designated as a National Historic Landmark
11-inch Mitchel telescope (0.27m, 1845)
16-inch Clark & Sons refractor (0.4m, 1904)
11-inch Merz & Mahler refractor (0.27m, 1845)
5 ⅜-inch Clark & Sons refractor (0.14m, 1860)
4-inch Clark & Sons refractor (0.1m, 1888)
5 ⅛-inch Fauth & Co. meridian telescope (0.13m, 1888)
6-inch Porter garden reflector (0.15m, 1923)
4-inch Bausch & Lomb refractor (0.1m, c. 1910-20)
Wes Ryle (astronomer)
Detroit Observatory
est. 1854
Ann Arbor, MI, USA
University of Michigan
Third largest refracting telescope in the world (1857)
Fitz Refracting Telescope (0.32m, 1857)
Meridian Circle Telescope (1854)
Austin Edmister (assistant director)
Dominion Astrophysical Observatory
est. 1918
Victoria, BC, Canada
National Research Council Canada
Second largest telescope in the world (1918)
Plaskett Telescope (1.8m reflector, 1918)
48-inch telescope (1.2m reflector, 1961)
Dennis Crabtree (vol-professional)
Website
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Elgin Observatory & Planetarium
est. 1910
Elgin, IL, USA
School District U-46
Kept time for Elgin National Watch Company (1910 – 1957)
Transmitted time signals to Chicago (1910 – 1957)
Used Arcturus to turn on Chicago World’s Fair lights (1933 – 4)
Listed on the National Register of Historic Places
3.5-inch Warner & Swasey transit telescope (0.09m, 1910)
4-inch Brashear telescope (0.1m, 1910)
Reifler sidereal and solar master clocks (1910)
Gartner level tester (1910)
Chronograph machines (1910 – )
Mechanical star light source (1930s)
Julien P. Friez & sons weather instruments (1910)
Peggy Hernández (teacher/director emerita)
Griffith Observatory
est. 1935
Los Angeles, CA, USA
City of Los Angeles
The most viewed telescope in the world (> 8.4 million visitors)
12-inch/9½-inch telescopes (0.3m/0.25m refractors, 1935/55)
Coelostat and Solar Telescopes (1935)
Ed Krupp (director)
Hamburg Observatory
est. 1802
Hamburg, Germany
Hamburg University
Largest aperture reflector in Europe (1911)
First (original) Schmidt telecope/camera (1930)
Discovery of largest NEO—1036 Ganymed (1924)
Compiled AGK2, AGK3, and Wendker's Radio Stars catalogs
Refsdal's gravitational lensing research (1963)
Creation and first headquarters of ESO (1962)
Listed as a monument of cultural and national importance
Large Double Refractor (0.6m, 1911)
1-m Reflector Telescope (1m, 1911)
Lippert Telescope (0.3m/0.3m/0.6m, 1911/1914/1974)
Equatorial refractor (0.26m, 1867)
Oskar Lühning Telescope (1.2m, 1975)
Salvador Mirror (0.4m, 1960)
Large Hamburg Schmidt (0.8m, 1954)—moved Calar Alto
Meridian circle (0.19m, 1909)
AG Astrograph (0.15m, 1924)
Zone astrograph (0.23m, 1971)
Gudrun Wolfschmidt (professor emerita)
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Harvard College Observatory
est. 1839
Cambridge, MA, USA
Harvard University
Largest telescope in the United States (1847)
Pioneer in astronomical photography
Leader in stellar classification, magnitudes, and positions
15-inch Great Refractor (0.38m, 1847)
Philippe Reekie (communication and outreach manager)
Website History Research Programs Observing Events Archives News
Theodor Jacobsen Observatory
est. 1895
Seattle, WA, USA
University of Washington
Listed in the Washington Heritage Register
6-inch refractor (0.15m, 1891)
Transit instruments
James Davenport (director of outreach)
Kashcheyev Radio Astronomy Lab
est. 1954
Kharkiv, Ukraine
Kharkiv National University of Radio Electronics
First radar detection of meteors in Ukraine (1954)
Development of the Automated Meteor Radio System (1957)
Large observational data set of meteors / meteoroids
Automated Meteor Radio System (MARS, 1957, damaged)
Svitlana Kolomiyets (scientific head / senior researcher)
Heidelberg-Königstuhl State Observatory
est. 1898
Heidelberg, Baden-Württemberg, Germany
University of Heidelberg
Prolific minor planet search program (> 750 by WWII)
Discovery of the Trojan Achilles (1906)
First minor planet discovered photographically (1891)
Early measurement of the rotation of a galaxy (1914)
Bruce double astrograph (0.40m refractors, 1900)
Waltz reflector (0.72m, 1906)
Kann refractor (0.20m, ca. 1894)
Wolf double astrograph (0.15m refractors, 1885)
Andreas Quirrenbach (director)
Lick Observatory
est. 1888
Mt. Hamilton, CA, USA
University of California Observatories
Largest refractor in the world (1888)
The world's first permanently occupied mountain-top observatory
36-inch James Lick ("Great Lick") Refractor (0.9m, 1888)
36-inch Crossley Reflector (0.9m, 1879/1896)
20-inch Carnegie Double Astrograph (0.5m refractors, 1941)
22-inch Tauchmann Reflector (0.5m, 1954)
120-inch Shane Telescope (3m reflector, 1959)
Coudé Auxiliary Telescope (0.6m reflector, 1969)
Matthew Shetrone (deputy director)
Website
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Live Cams
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Lowell Observatory
est. 1894
Flagstaff, AZ, USA
Mormon Lake, AZ, USA
Discovery of Pluto (1930)
24-inch Clark Telescope (0.6m refractor, 1896)
13-inch A. L. Lowell Astrograph (0.3m refractor, 1929)
W. Lowell Putnam (trustee)
Website
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Research
Visiting
Stargazing
Programs
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Leander McCormick Observatory
est. 1884
Charlottesville, VA, USA
University of Virginia
Second largest refractor in the world (with USNO, 1884)
Largest telescope in the U.S. (with USNO, 1884)
Largest extant Alvan Clark & Sons mount and drive (1884)
Leader in stellar parallax measurements (1914–1994)
Pioneer in cataloging nearby M dwarf stars (1937–1958)
Listed on the National Register of Historic Places
Listed on the Virginia Landmarks Register
26-inch Clark Refractor (0.66m, c.1877) on Clark mount
6-inch Clark Refractor on Saegmuller mount (0.15m, 1895)
10-inch Astrograph (0.25m, 1937)
3-inch Fauth & Co meridian telescope (1884)
Steven Majewski (UVA astronomy dept. chair)
McDonald Observatory
est. 1939
Fort Davis, TX, USA
University of Texas
Second largest telescope in the world (1939)
Third largest telescope in the world (1968)
Otto Struve Telescope (2.1m reflector, 1939)
Harlan J. Smith Telescope (2.7m reflector, 1968)
0.8m telescope (reflector, 1970)
0.9m telescope (reflector, 1956)
Katie Kizziar (asst. director for education & outreach)
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Maria Mitchell Observatory
est. 1902
Nantucket, MA, USA
Maria Mitchell Association
Founded in honor of the first American female astronomer
First female director of a private observatory in the US
2 ¾-inch Dollond refractor (0.07m, ca. 1830s)
5-inch Alvan Clark telescope (0.13m, 1859)
7 ½-inch photographic refractor (0.19m, ca. 1913)
Joanna Roche (executive director)
Website History Research Visiting Stargazing Programs Media Archives Calendar
Milwaukee Astronomical Society
est. 1932
New Berlin, WI, USA
Over 1.5 million AAVSO observations contributed since 1929
Founding organization of the Astronomical League
Project Moonwatch station—Sputnik IV re-entry prediction
Pioneer site for grazing lunar occultation observations
Among the largest amateur astronomy societies in the US
12.5-inch Ralph H. Buckstaff telescope (0.32m reflector, 1921)
12.5-inch Edward A. Halbach telescope (0.32m reflector, 1977)
Matthew Ryno (president)
Website Visiting History Research Observing Events Archives News Media
Mount Wilson Observatory
est. 1904
Mt. Wilson, CA, USA
Mount Wilson Institute
Largest telescopes in the world (1908 and 1917)
First extragalactic distance measurements
Early cosmic expansion estimates
First evidence of dark matter
Discovery of different stellar populations
100-inch Hooker Telescope (2.5m reflector, 1917)
60-inch telescope (1.5m reflector, 1908)
60-ft (18m) Snow Solar Telescope (1905)
150-ft (46m) solar tower (1912)
Timothy Thompson (science director)
Website History Visiting Observing Programs Events Live Cams Tour
Palomar Observatory
est. 1948
Palomar Mountain, CA, USA
Caltech
Largest telescope in the world (1949)
Largest Schmidt in the world (1948)
Palomar sky surveys (1958 and 2000)
Discovery of quasars (1963)
Discovery of Eris (2005) and other TNOs
200-inch Hale Telescope (5m reflector, 1949)
48-inch Samuel Oschin Telescope (1.2m Schmidt, 1948)
18-inch telescope (0.46m Schmidt, 1936)
60-inch telescope (1.5m reflector, 1970)
Andy Boden (deputy director)
Website History Research Visiting Tour Exhibits Live Cams Archives News
Pic du Midi Observatory
est. 1878
Pic du Midi de Bigorre, France
Paul Sabatier University (Toulouse III)
World's first high-mountain observatory
Formally discredited Martian canal theory
Mapped the surface of the Moon for the Apollo missions
Detailed Venus and Mars atmospheric studies
Discovery of Saturn's moon Helene
Invention of the coronagraph
Lyot coronagraph (1935)
Jean Rösch telescope (0.5m refractor, 1961)
T60 telescope (0.6m reflector, 1910/1945)
T1 telescope (1m reflector, 1963)
Rémi Cabanac (science director)
Website 1 Website 2 History Research Visiting Stargazing Programs Exhibits Live Cams News Events
Sommers-Bausch Observatory
est. 1953
Boulder, CO, USA
University of Colorado
Historic headquarters of the High Altitude Observatory
Complementary to coronagraph at the Climax Observatory
Pioneer in ground-based CCD astronomy
24-inch Boller & Chivens telescope (0.6m reflector, 1973)
Gleason heliostat (1973)
10 ½-inch Bausch telescope (0.26m refractor, 1953)
Rose Smith (observatory manager)
University of Illinois Observatory
est. 1896
Urbana, IL, USA
University of Illinois
Pioneer in electric detectors and astronomical photometry
First electric light curve of the Moon
Listed on the National Register of Historic Places
Designated as National Historic Landmark
12-inch equatorial refractor (0.3m, 1896)
Bryan Dunne (director)
Van Vleck Observatory
est. 1914
Middletown, CT, USA
Wesleyan University
Pioneering, multi-decade stellar parallax program
20-inch Alvan Clark Great Refractor (0.5m, 1922)
24-inch Perkin Telescope (0.6m reflector, 1966)
Roy Kilgard (associate professor)
Vatican Observatory
est. 1577
Albano Laziale RM, Italy
Tucson, AZ, USA
Mt. Graham, AZ, USA
Vatican City State
One of the oldest observatories in the world
Establishment of the Gregorian calendar
Participation in the Carte du Ciel survey
Carte du Ciel Telescope (0.33m double refractor, 1891/1942)
Schmidt telescope (0.65m, 1942)
Zeiss visual refractor telescope (0.4m, 1935)
Zeiss double astrograph (0.6m reflector/0.4m refractor, 1935)
Paul Gabor (vice director)
Website 1 Website 2 History Research Programs Visiting Tour 1 Tour 2 Media Events News Podcasts Meteor Cam
Washburn Observatory
est. 1878
Madison, WI, USA
University of Wisconsin-Madison
Third largest telescope in the United States (1878)
15.6-inch Clark refractor (0.4m, 1878)
James Lattis (Space Place director)
Yerkes Observatory
est. 1892
Williams Bay, WI, USA
Yerkes Future Foundation
Largest refracting telescope in the world (1897)
First modern astrophysical observatory
Pioneer in adaptive optics
40-inch refractor (1m, 1897)
41-inch reflector (1m, 1968)
24-inch reflector (0.6m, 1964)
Amanda Bauer (deputy director)
Several of our facilities have virtual tours in video or interactive form. Below are links to these media:
