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{{Use American English|date=July 2025}}
{{Infobox observatory
| name = McDonald Observatory
| image =
| caption = The observatory from the southeast. The Hobby–Eberly Telescope on Mt. Fowlkes (left) and the Harlan J. Smith and Otto Struve Telescopes on Mt. Locke (right).
| location = [[Jeff Davis County, Texas]]
}}
'''McDonald Observatory''' is an [[astronomical observatory]] located near the [[unincorporated area|unincorporated community]] of [[Fort Davis, Texas|Fort Davis]] in [[Jeff Davis County, Texas]], United States. The facility is located on Mount Locke in the [[Davis Mountains]] of [[West Texas]], with additional facilities on Mount Fowlkes, approximately {{Convert|1.3|km|mi|sp=us}} to the northeast.<ref name=MO-ABT />  The observatory is part of [[The University of Texas at Austin]]. It is an organized research unit of the [[University of Texas at Austin College of Natural Sciences|College of Natural Sciences.]]

The observatory produces ''[[StarDate (radio)|StarDate]]'', a daily [[radio syndication|syndicated radio]] program consisting of short segments related to astronomy that airs on both [[National Public Radio]] and commercial radio stations — about 400 affiliates in all.

==History==
[[File:Mcdonald Observatory.jpg|thumb|McDonald Observatory]]

McDonald Observatory was originally endowed by the Texas banker [[William Johnson McDonald]] (1844&ndash;1926), who left about $1 million — the bulk of his fortune — to The University of Texas at Austin to endow an astronomical observatory. Edwin Hockaday Fowlkes, step-son of the land's original owner John Chandler Prude, donated the land to the University of Texas to build the observatory. The provision of the will was challenged by McDonald's relatives, but after a long legal fight, the university received about $800,000 from the estate and construction began at Mt. Locke. The then-unnamed Otto Struve Telescope was dedicated on May 5, 1939,<ref>{{Cite web|last=The Film & Video Archive of the McDonald Observatory|title=Franklin Mountains and Dedication Ceremony (1939)|url=https://texasarchive.org/2019_02356|website=Texas Archive of the Moving Image}}</ref> and at that time was the second largest telescope in the world. McDonald Observatory was operated under contract by [[The University of Chicago]] until the 1960s, when control was transferred to The University of Texas at Austin under the direction of [[Harlan J. Smith]].<ref name=tsha>{{Citation |last=Evans |first=David S. |title=University of Texas at Austin McDonald Observatory |publisher=Texas State Historical Association |url=http://www.tshaonline.org/handbook/online/articles/kcu28}}</ref>

Research today at the McDonald Observatory encompasses a wide variety of topics and projects, including the search for and understanding of [[planetary systems]], stars and stellar [[spectroscopy]], the [[interstellar medium]], [[extragalactic astronomy]], and [[theoretical astronomy]]. The Hobby-Eberly Telescope Dark Energy Experiment, or HETDEX,<ref>[http://hetdex.org HETDEX]</ref> is a multi-year undertaking to decode the nature of [[dark energy]].<ref name=UT-RSCH />

'''Directors'''<ref name=tsha />
* [[Otto Struve]] (1932–1950)
* [[Gerard Peter Kuiper]] (Sept. 1947–Dec. 1949, Sept. 1957–Mar. 1959)
* [[Bengt Georg Daniel Strömgren]] (Jan. 1951–Aug. 1957)
* [[William Wilson Morgan]] (Apr. 1959–Aug. 1963)
* [[Harlan James Smith]] (Sept. 1963–1989)
* {{ill|Frank N. Bash|qid=Q72783063|short=yes}} (1989–2003)<ref>{{Citation |title=McDonald Observatory Visitors Center Named for Former Director Dr. Frank N. Bash |date=2006-07-17 |publisher=The University of Texas McDonald Observatory |url=http://mcdonaldobservatory.org/news/releases/2006/0717.html}}</ref>
* [[David L. Lambert]] (2003–2014)<ref>{{Citation |title=American Astronomical Society Confers Highest Honor on McDonald Observatory Director David Lambert |date=2007-02-05 |publisher=The University of Texas McDonald Observatory |url=http://mcdonaldobservatory.org/news/releases/2007/0205.html}}</ref>
* [[Taft E. Armandroff]] (2014–present)<ref>{{Citation |title=Leading Astronomer Taft Armandroff Appointed New Director of McDonald Observatory |date=2014-01-14 |publisher=The University of Texas McDonald Observatory |url=http://mcdonaldobservatory.org/news/releases/2014/01/14}}</ref>

==Observatory==
[[Image:HET Dome.jpg|thumb|right|Dome of the 10 m Hobby-Eberly Telescope. It houses one of the [[List of largest optical reflecting telescopes|largest optical telescopes in the world]].]]

McDonald Observatory is equipped with a wide range of instrumentation for [[imaging science|imaging]] and [[spectroscopy]] in the [[visible-light astronomy|optical]] and [[infrared]] spectra, and operates the first [[lunar laser ranging]] station.  It works closely with the [[astronomy]] department of The University of Texas at Austin while maintaining administrative autonomy.{{Citation needed|date=January 2012}}  The high and dry peaks of the Davis Mountains make for some of the darkest and clearest night skies in the region and provide excellent conditions for astronomical research.{{Citation needed|date=January 2012|reason=site characterization info}}

[[File:Electric motors and position sensors at the Otto Struve Telescope at the McDonald Observatory, Texas.JPG|thumb|Electric motors and position sensors at the Otto Struve Telescope at the McDonald Observatory, Texas]]

The [[Otto Struve Telescope]], dedicated in 1939, was the first large telescope built at the observatory.<ref name=UT-OST /><ref name=MO-OST />  It is located on Mt. Locke at an altitude of {{Convert|2070|m|ft|sp=us|abbr=on}}. The summit of Mt. Locke, accessed by [[Texas State Highway Spur 78|Spur 78]], is the highest point on Texas highways.<ref name=PHOTO />  The [[Harlan J. Smith Telescope]], also on Mt. Locke, was completed in 1968.<ref name=UT-HJST /><ref name=MO-HJST />

The [[Hobby-Eberly Telescope]] (HET), dedicated in late 1997, is located on the summit of Mt. Fowlkes at {{Convert|2030|m|ft|sp=us|abbr=on}} above sea level.<ref name=UT-HET />  It is operated jointly by The University of Texas at Austin, [[Pennsylvania State University]], [[Ludwig Maximilian University of Munich]], and [[Georg-August University of Göttingen]].<ref name=MO-HET />  As of 2019, after upgrades the HET is tied with the [[W.M. Keck Observatory|Keck Telescopes]] as the second or third [[List of largest optical reflecting telescopes|largest telescope]] in the world.  However, its cost was about 20% that of other similarly sized telescopes in use today due to its optimization for [[spectroscopy]].

Additionally, The University of Texas at Austin is a founding partner of the international collaboration to build the [[Giant Magellan Telescope]]. McDonald Observatory administrators, scientists, and engineers are heavily involved in the endeavor. Director Taft Armandroff currently serves as Vice Chair to the GMT Board of Directors, and has served as chair.

==Telescopes==
[[Image:McDonald Observatory 82 & 107-inch Telescopes.JPG|thumb|right|Domes of the 2.1 m Otto Struve Telescope (left) and 2.7 m Harlan J. Smith Telescope (right)]]

Currently, the observatory operates four [[research]] telescopes at its West Texas site:

<!--NOTE: Make sure to use the units the telescope was built to match because the convert template "operation" does not commute; for example, if the telescope was built to be 82", the convert template shows 2.1 m, which is a rounded value is a rounded value but 2.1m converted to inches gives 83" which is not the size of the telescope.-->
* {{Convert|10|m|in|abbr=on}} [[Hobby-Eberly Telescope]] on Mt. Fowlkes
* {{Convert|107|in|m|abbr=on|order=flip}} [[Harlan J. Smith Telescope]] on Mt. Locke
* {{Convert|82|in|m|abbr=on|order=flip}} [[Otto Struve Telescope]] on Mt. Locke
* {{Convert|30|in|m|abbr=on|order=flip|sigfig=1}} large format imaging [[telescope]] on Mt. Locke<ref name=UT-08MT /><ref name=MO-08MT />

A {{Convert|36|in|m|abbr=on|order=flip|sigfig=1}} telescope, formerly used for research, is now used for visitor programs.<ref name=UT-09MT /><ref name=MO-09T />

===Tenant telescopes===

The two peaks also host a number of other instruments:

* The {{Convert|1.2|m|in|abbr=on}} Monitoring Network of Telescopes ([[MONET/North]]) Telescope on Mt. Locke is a companion to the {{ill|MONET/South|qid=Q115616954|short=yes}} at the [[South African Astronomical Observatory]] in [[Sutherland, Northern Cape|Sutherland]], and was built by [[Halfmann Teleskoptechnik]].<ref name=MONET />
* Two {{Convert|1.0|m|in|abbr=on}} telescopes and one {{Convert|0.4|m|in|abbr=on}} telescope located on Mt. Fowlkes are part of the [[Las Cumbres Observatory Global Telescope Network]].
* A {{Convert|0.5|m|in|abbr=on}} [[Ritchey-Chretien]] reflector owned by [[Boston University]] on Mt. Locke is used for optical [[aeronomy]].<ref name=BU20 />
* The {{Convert|0.4|m|in|abbr=on}} [[Robotic Optical Transient Search Experiment]] (ROTSE) reflector on Mt. Fowlkes is used to search for the optical signature of [[gamma-ray bursts]].<ref name=ROTSE />

===Former telescopes===

* The {{Convert|4.9|m|ft|abbr=on}} Millimeter Wave Observatory (MWO) [[radio telescope]] operated on Mt. Locke until 1988.<ref name=1990REPT />  MWO was a joint project between the UT Department of Astronomy and the Department of Electrical Engineering.  The site of the dish antenna is now occupied by the ''BLOOMhouse'', the UT [[University of Texas School of Architecture|School of Architecture]]'s entry in the 2007 [[Solar Decathlon]], which is now used for staff housing.<ref name=BLOOM />
* The McDonald Laser Ranging System (MLRS) used a {{Convert|0.76|m|in|abbr=on}} telescope on Mt. Fowlkes from 1982 to 2019 for [[satellite laser ranging]] and [[lunar laser ranging]].<ref>[https://ilrs.gsfc.nasa.gov/about/news/Past_News.html#2019 Lightning strikes the McDonald Laser Ranging Station (MLRS) in Texas] ILRS News 9/30/2019</ref>

==Climate==
The observatory experiences a [[semi-arid climate]] ([[Köppen climate classification|Köppen]] ''BSk'') with cool, dry winters and hot, wetter summers.
*Coordinates: {{Coord|30.70528|N|104.02333|W}}
*Elevation: {{Convert|6790|ft|m|0}}<ref name="US COOP Stations">{{Cite web|publisher=[[Western Regional Climate Center]], [[Desert Research Institute]]|title=US COOP Station Map|url=http://www.wrcc.dri.edu/coopmap/|access-date=May 3, 2015|archive-date=May 3, 2015|archive-url=https://web.archive.org/web/20150503151618/http://www.wrcc.dri.edu/coopmap/|url-status=dead}}</ref>
{{Weather box
|location = Mount Locke, Texas (Jan 1, 1935–Mar 31, 2013)
|single line = Yes
|Jan record high F = 80
|Feb record high F = 79
|Mar record high F = 88
|Apr record high F = 94
|May record high F = 96
|Jun record high F = 104
|Jul record high F = 100
|Aug record high F = 104
|Sep record high F = 96
|Oct record high F = 94
|Nov record high F = 82
|Dec record high F = 80
|year record high F = 104
|Jan high F = 53.5
|Feb high F = 56.9
|Mar high F = 63.7
|Apr high F = 71.4
|May high F = 78.6
|Jun high F = 84.5
|Jul high F = 82.7
|Aug high F = 81.3
|Sep high F = 76.6
|Oct high F = 70.5
|Nov high F = 61.2
|Dec high F = 54.4
|year high F = 69.6
|Jan mean F=42.7
|Feb mean F=45.4
|Mar mean F=51.0
|Apr mean F=58.3
|May mean F=65.5
|Jun mean F=71.4
|Jul mean F=70.8
|Aug mean F=69.8
|Sep mean F=65.5
|Oct mean F=59.3
|Nov mean F=50.0
|Dec mean F=44.0
|year mean F=57.8
|Jan low F = 32.0
|Feb low F = 33.9
|Mar low F = 38.2
|Apr low F = 45.2
|May low F = 52.4
|Jun low F = 58.2
|Jul low F = 58.9
|Aug low F = 58.4
|Sep low F = 54.4
|Oct low F = 48.0
|Nov low F = 38.7
|Dec low F = 33.6
|year low F = 46.0
|Jan record low F = -10
|Feb record low F = -6
|Mar record low F = 4
|Apr record low F = 11
|May record low F = 26
|Jun record low F = 36
|Jul record low F = 40
|Aug record low F = 40
|Sep record low F = 29
|Oct record low F = 13
|Nov record low F = 8
|Dec record low F = -2
|year record low F = -10
|precipitation colour=green
|Jan precipitation inch = 0.68
|Feb precipitation inch = 0.49
|Mar precipitation inch = 0.40
|Apr precipitation inch = 0.50
|May precipitation inch = 1.63
|Jun precipitation inch = 2.49
|Jul precipitation inch = 3.83
|Aug precipitation inch = 3.69
|Sep precipitation inch = 2.95
|Oct precipitation inch = 1.61
|Nov precipitation inch = 0.61
|Dec precipitation inch = 0.60
|year precipitation inch = 19.46
|Jan snow inch=1.9
|Feb snow inch=0.8
|Mar snow inch=0.2
|Apr snow inch=0.1
|May snow inch=0.0
|Jun snow inch=0.0
|Jul snow inch=0.0
|Aug snow inch=0.0
|Sep snow inch=0.0
|Oct snow inch=0.1
|Nov snow inch=0.4
|Dec snow inch=1.2
|year snow inch=4.7
|unit precipitation days=0.001
|Jan precipitation days=3.75
|Feb precipitation days=3.13
|Mar precipitation days=2.62
|Apr precipitation days=2.77
|May precipitation days=5.93
|Jun precipitation days=8.75
|Jul precipitation days=12.00
|Aug precipitation days=11.56
|Sep precipitation days=9.32
|Oct precipitation days=5.91
|Nov precipitation days=2.94
|Dec precipitation days=3.29
|year precipitation days=71.45
|source 1 = [[Western Regional Climate Center]], [[Desert Research Institute]]<ref name="WRCC">{{Cite web|publisher=Western Regional Climate Center, Desert Research Institute|title=MOUNT LOCKE, TEXAS (416104), Period of Record Monthly Climate Summary|url=http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?tx6104|access-date=May 3, 2015}}</ref>
|date=May 2015
}}

==Visiting==
[[Image:USA harlan j smith telescope TX.jpg|thumb|Inside the dome of the Harlan J. Smith telescope during a guided tour]]

The {{ill|Frank N. Bash Visitors Center|qid=Q72781778|short=yes}}, located between Mt. Locke and Mt. Fowlkes, includes a gift shop and interactive exhibit hall. The Visitors Center conducts daily live solar viewings in a large theater and tours of the observatory's largest telescopes.  It also hosts evening [[star party|star parties]], every Tuesday, Friday, and Saturday evening which allow visitors to look through numerous telescopes of various sizes in the Rebecca Gale Telescope Park.<ref name=MO-FBNV />

Special Viewing Nights, during which visitors can stay on-site (not required for the programs) and view directly through eyepieces on the 0.9 m and Struve (2.1m) telescopes, are held on a reservation-only basis.

==Gallery==
<gallery>
Image:McDonaldObservatoryEntranceSign.JPG|Entrance to the observatory
Image:FrankBashVisitorCenter.JPG|Frank N. Bash Visitors Center
Image:McDonald Sun Dial.JPG|McDonald Observatory's Visitor Center's sun dial
Image:107-inch at dusk.JPG|Harlan J. Smith Telescope preparing for observations
File:McDonald Observatory Historical Marker.jpg|Texas historical marker
File:Mount Locke Texas Highways.jpg|Texas highway marker at McDonald Observatory 
</gallery>

==See also==
* [[List of astronomical observatories]]

==References==
{{Reflist|30em|refs=

<ref name=MO-ABT>{{Cite web |title=About {{!}} McDonald Observatory |url=http://www.mcdonaldobservatory.org/about |publisher=McDonald Observatory |access-date=2012-01-10}}</ref>

<ref name=UT-RSCH>{{Cite web |title=UT Astronomy - Research |url=http://www.as.utexas.edu/astronomy/research/research.html |publisher=University of Texas at Austin Astronomy Program|access-date=2012-01-10}}</ref>

<ref name=UT-OST>{{Cite web |title=McDonald Observatory - 2.1-m Telescope |url=http://www.as.utexas.edu/mcdonald/facilities/2.1m/2.1.html |publisher=University of Texas at Austin Astronomy Program|access-date=2012-01-10}}</ref>

<ref name=MO-OST>{{Cite web |title=The Otto Struve Telescope {{!}} What Are Astronomers Doing? {{!}} McDonald Observatory |url=http://mcdonaldobservatory.org/research/telescopes/telescope.php?t_id=17 |publisher=McDonald Observatory |access-date=2012-01-10}}</ref>

<ref name=PHOTO>{{cite web |title=The Highest Point on Texas Highways |last=Dindinger |first=Peter. |url=https://www.flickr.com/photos/pdtbird21/3856752991/ |date=25 August 2009 |access-date=2012-01-10}}</ref>

<ref name=UT-HJST>{{Cite web |title=McDonald Observatory - 2.7 m Telescope |url=http://www.as.utexas.edu/mcdonald/facilities/2.7m/2.7.html |publisher=University of Texas at Austin Astronomy Program|access-date=2012-01-10}}</ref>

<ref name=MO-HJST>{{Cite web |title=The Harlan J. Smith Telescope {{!}} What Are Astronomers Doing? {{!}} McDonald Observatory |url=http://mcdonaldobservatory.org/research/telescopes/telescope.php?t_id=16 |publisher=McDonald Observatory |access-date=2012-01-10}}</ref>

<ref name=UT-HET>{{Cite web |title=Hobby-Eberly Telescope |url=http://www.as.utexas.edu/mcdonald/het/het.html |publisher=University of Texas at Austin Astronomy Program|access-date=2012-01-10}}</ref>

<ref name=MO-HET>{{Cite web |title=The Hobby-Eberly Telescope {{!}} What Are Astronomers Doing? {{!}} McDonald Observatory |url=http://mcdonaldobservatory.org/research/telescopes/telescope.php?t_id=1 |publisher=McDonald Observatory |access-date=2012-01-10}}</ref>

<ref name=UT-08MT>{{Cite web |title=UT Astronomy - 0.8 m Telescope |url=http://www.as.utexas.edu/mcdonald/facilities/0.8m/0.8.html |publisher=University of Texas at Austin Astronomy Program|access-date=2012-01-10}}</ref>

<ref name=MO-08MT>{{Cite web |title=0.8-meter Telescope {{!}} What Are Astronomers Doing? {{!}} McDonald Observatory |url=http://mcdonaldobservatory.org/research/telescopes/telescope.php?t_id=18 |publisher=McDonald Observatory |access-date=2012-01-10}}</ref>

<ref name=UT-09MT>{{Cite web |title=UT Astronomy - 0.9 m Telescope |url=http://www.as.utexas.edu/mcdonald/facilities/0.9m/0.9.html |publisher=University of Texas at Austin Astronomy Program|access-date=2012-01-10}}</ref>

<ref name=MO-09T>{{Cite web |title=0.9-meter telescope {{!}} What Are Astronomers Doing? {{!}} McDonald Observatory  |url=http://mcdonaldobservatory.org/research/telescopes/telescope.php?t_id=22 |publisher=McDonald Observatory |access-date=2012-01-10}}</ref>

<ref name=MONET>{{Cite web |title=Welcome to MONET / Astronomie & Internet |url=http://monet.uni-goettingen.de/foswiki |publisher=[[University of Göttingen]] |access-date=2010-10-02 |archive-date=2017-03-18 |archive-url=https://web.archive.org/web/20170318114843/http://monet.uni-goettingen.de/foswiki/ |url-status=dead }}</ref>

<ref name=BU20>{{Cite web|title=BU Imaging Science - The Boston University 20-inch Telescope at McDonald Observatory|url=http://sirius.bu.edu/planetary/mcdonald.html|publisher=Boston University Center For Space Physics|access-date=2012-01-10}}</ref>

<ref name=ROTSE>{{Cite web|title=ROTSE Home Page|url=http://www.rotse.net/|publisher=Robotic Optical Transient Search Experiment|access-date=2012-01-10}}</ref>

<ref name=1990REPT>{{cite journal |bibcode=1990BAAS...22R.620. |title=University of Texas at Austin, Department of Astronomy, Austin, Texas 78712-1083, McDonald Observatory, Fort Davis, Texas 79734. Report for the period 1 Sep 1988 - 31 Aug 1989 |volume=22 |year=1990 |pages=620 |journal=Bulletin of the Astronomical Society|issue=1 }}</ref>

<ref name=BLOOM>{{cite web|last=Johnson|first=Rebecca|title=McDonald Observatory gets Solar BLOOMhouse « Know|url=http://www.utexas.edu/know/2008/05/01/bloomhouse-feature/|archive-url=https://archive.today/20121210133032/http://www.utexas.edu/know/2008/05/01/bloomhouse-feature/|url-status=dead|archive-date=December 10, 2012|access-date=2012-01-30|date=2008-05-01}}</ref>

<ref name=MO-FBNV>{{Cite web |title=McDonald Observatory {{!}} Public Programs, Star Parties, Tours and Special Viewing Night |url=http://mcdonaldobservatory.org/visitors/programs/ |publisher=McDonald Observatory |access-date=2012-01-10 |url-status=dead |archive-url=https://web.archive.org/web/20111217053024/http://mcdonaldobservatory.org/visitors/programs/ |archive-date=2011-12-17 }}</ref>
}}

==External links==
{{Commons category|McDonald Observatory}}
*[http://mcdonaldobservatory.org/ McDonald Observatory public site]
*[http://www.as.utexas.edu/mcdonald/ McDonald Observatory at the University of Texas at Austin]
*[http://stardate.org/ ''StarDate''] and [http://radiouniverso.org/ Universo]
*[http://cleardarksky.com/c/McDonaldObTXkey.html?1 McDonald Observatory Clear Sky Chart] – forecasts of observing conditions
*[https://texasarchive.org/2019_02356 1939 Film of the dedication ceremony for McDonald Observatory]

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[[Category:Astronomical observatories in Texas]]
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[[Category:Buildings and structures in Jeff Davis County, Texas]]
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