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Ladd Observatory

Organization	Brown University
Location	Providence, Rhode Island, US
Coordinates	41°50′20″N 71°23′57″W / 41.83889°N 71.39917°W / 41.83889; -71.39917
Altitude	205 feet (62.5 m)
Weather	See the Clear Sky Chart
Established	October 21, 1891 (1891-10-21)
Website	brown.edu/ladd
Telescopes
Brashear / Saegmuller 12" refractor Saegmuller 3" meridian circle Ladd Observatory U.S. National Register of Historic Places Show map of Rhode IslandShow map of the United States Location 210 Doyle Ave. Providence, Rhode Island, US Coordinates 41°50′20″N 71°23′57″W / 41.83889°N 71.39917°W / 41.83889; -71.39917 Built 1891 Architect Stone, Carpenter & Willson Architectural style Classical Revival NRHP reference No. 93000583 Added to NRHP June 6, 2000
Location of Ladd Observatory
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Ladd Observatory is an astronomical observatory at Brown University in Providence, Rhode Island. Founded in 1891, it was primarily designed for student instruction and research. The facility operated a regional timekeeping service. It was responsible for the care and calibration of clocks on campus including one at Carrie Tower and another that rang the class bell at University Hall. Meteorological observations were made there from the time the building opened using recording weather instruments.

In addition to general astronomy courses it was also used for teaching civil engineering topics such as geodesy. Nautical science subjects, including celestial navigation, were taught there during the First World War.

Ladd began a regular schedule of open nights for public viewing in 1930. This led to the creation of the Skyscrapers amateur astronomy society in 1932 which regularly met at Ladd. The Skyscrapers then acquired the Seagrave Observatory in 1936 which was then used as a meeting place. Amateur astronomers from the group continued to volunteer at Ladd and also participated in Brown University solar eclipse expeditions. Members constructed a Schmidt camera for the 1937 Brown eclipse expedition.

Ladd was added to the National Register of Historic Places in 2000. It continues to be used by the Department of Physics at Brown for astronomy instruction. It is regularly open to the public as a science center and technology museum.

Construction

The observatory is named for benefactor Herbert W. Ladd who offered to fund the construction in the spring of 1889. The building was designed by the Providence-based firm of Stone, Carpenter & Willson in the Classical Revival style. The selected site was the highest point in Providence at the time, on what was once known as Tintop Hill on the East Side. Construction began in May 1890 and the building was dedicated on October 21, 1891. The total cost of construction and equipping the facility in 1891 was US$40,000, equivalent to $1,400,000 in 2023.

Telescopes

The primary telescope is a refractor with a 12-inch (300 mm) aperture objective and focal length of 15 feet (4.6 m). The lens was figured by John Brashear following the design of Charles S. Hastings. The crown glass was made by Mantois of Paris and the flint glass by the optical works at Jena in Germany. The equatorial mount and mechanical clock drive were made by George N. Saegmuller. This telescope was used for scientific work such as lunar occultation timings to make a more precise determination of the orbit of the Moon. Instruments such as a filar micrometer could be attached to the telescope.

Another telescope, a 3-inch (76 mm) meridian circle instrument, also made by Saegmuller, was used for observations related to timekeeping. Similar, but smaller, instruments were used for student instruction.

Timekeeping

As a number of other observatories did in the late 19th century Ladd provided an accurate regional timekeeping service by transmitting a time signal via telegraph wire. Observations of select stars were made with the meridian circle instrument as the star transited (or crossed) the meridian. This data was then used to calibrate a high quality pendulum clock set to keep sidereal time. Calculations were then performed to convert sidereal time to local standard time. A second clock keeping standard time was equipped with a telegraphic break circuit mechanism to automatically generate the time signals. These precision clocks were known as astronomical regulators. Timekeeping instruments used at Ladd include regulators designed by Robert Molyneux, Edward Howard, Hezekiah Conant, and Sigmund Riefler.

Prior to the Ladd time service the city relied on time signals from either Harvard College Observatory or the United States Naval Observatory that were transmitted via Western Union Telegraph wires. In many cases these signals were found to be inaccurate due to transmission delay or accidents. Time signals from Ladd were first sent on September 12, 1893. The observatory sold these time signals to Rhode Island Electric Protective (RIEP) company, a local fire and burglar alarm firm. The signals from Ladd were redistributed to RIEP customers including "jewelers" (i.e. clockmakers) who repaired and calibrated watches.

The signals were also used to directly control a clock network of several hundred slave clocks in various business offices. The revenue that the university received from the time signal service in 1906 was US$200 (equivalent to $6,800 in 2023) per year. Another telegraph wire connected the observatory to the Fire Department at City Hall which was used to signal the accurate time to the community by fire alarm bells at noon and 8:30 p.m. every day. Time signals from Ladd were also used to synchronize the regulator used to ring the bell in the cupola of University Hall on the main campus. The bell marked the beginning and end of class periods.

Ladd first received experimental wireless time signals from the Naval Observatory in November 1913. The purpose of the experiment was to measure the difference in longitude between Washington and Providence. The signals were transmitted by the Navy radio facility NAA in Arlington, Virginia. In 1915 Brown installed a sophisticated "wireless plant" consisting of a 450-foot-long (140 m) antenna strung between a tower on University Hall and another tower on Maxcy Hall. The operator's station with transmitting and receiving equipment was located in the basement of Wilson Hall, a building midway between the two towers. Primarily intended for engineering instruction and physics experimentation it was also used to receive the time signals from Arlington. On November 24, 1916 the transit instrument observations were discontinued and the clocks were instead calibrated by the NAA signals. The transit observations resumed on April 10, 1917 due to a US government order to dismantle the radio set at Ladd when the U.S. entered the First World War. These calibration observations continued through October 16, 1919.

Calibration by Naval Observatory time signals from radio station WWV resumed after the war ended. These early transmissions were longwave, so called due to the long wavelength. Frequencies, and corresponding wavelengths, from 15 kilohertz (20,000 m) to 150 kilohertz (2,000 m) were used. These transmissions required special equipment such as the installation at Wilson Hall to receive them. By the 1930s it had become common to use a simple and inexpensive shortwave radio of the kind used to receive broadcast programs. This radio could also be used to receive time signal transmissions from Greenwich, Paris, and Berlin. The radio was directly wired to the clock circuits to allow recording the time signals.

The sirens on fire stations continued to sound at noon using the time signals from Ladd until at least 1955. Clocks in a number of buildings in Providence were regulated using the signals from Ladd late into the 20th century. After determining no one was receiving the time signals, the transmissions were discontinued in 1973.

Associations

Scientists affiliated with the observatory include Winslow Upton, Frank Washington Very, Frederick Slocum, Robert Horace Baker, and Charles H. Smiley. Notable graduates from Brown or Pembroke who performed work at Ladd include Slocum (A.B. 1895, Ph.D. 1898), Leah Allen (A.B. 1907), and Harlan True Stetson (B.S. 1912).

H. P. Lovecraft, author of weird fiction, had free access to the observatory for several years. He wrote astronomy articles for Providence newspapers between 1906 and 1918 based upon his study there.

See also

• List of astronomical observatories
• List of Brown University buildings
• List of largest optical refracting telescopes

References

1. "OBSERVER". NGS Data Sheet. National Geodetic Survey. 1999. Retrieved 11 December 2019.
2. Donnelly, Marian Card (Winter 1960). "Astronomical Observatories in New England". Old-Time New England. 50 (179). Society for the Preservation of New England Antiquities: 72–80. Retrieved 7 January 2016.
3. ^ Upton, Winslow (December 1891). "The Ladd Observatory". Sidereal Messenger. pp. 502–504. Retrieved 12 December 2019.
4. ^ Upton, Winslow (October 21, 1908). "Report of the Director of the Observatory". Annual Report of the President to the Corporation of Brown University. p. 63. Retrieved 13 December 2019.
5. Upton, Winslow (October 1913). "Report of the Director of the Ladd Observatory". Annual Report of the President to the Corporation of Brown University. Providence. Retrieved 12 December 2019.{{cite book}}: CS1 maint: location missing publisher (link)
6. ^ Smiley, Charles H. (April 1939). "Ladd Observatory at Brown University". The Sky. American Museum of Natural History. pp. 8–9, 22–23.
7. Huestis, David A. (July 22, 2014). "Seagrave Memorial Observatory centennial (1914-2014)". Astronomy Magazine. Kalmbach Publishing Co. Retrieved 7 January 2016.
8. "National Register Asset Details". The Focus Digital Asset Management System. National Park Service. January 1992. Retrieved 6 February 2016.
9. ^ "Herbert W. Ladd, Ex-Governor, Dead". Providence, Rhode Island: The Providence Sunday Journal. 30 November 1913. p. 1.
10. Robinson, Arnold N.; Swanson, Carla (June 6, 2000). National Register of Historic Places Registration Form: Ladd Observatory (PDF) (Report). National Park Service.
11. Umbricht, Michael L. (July 10, 2017). "Tin-top Hill". Ladd Observatory Blog. Brown University Physics. Retrieved 11 December 2019.
12. "Neutaconkanut". Providence Sunday Journal. September 11, 1898. p. 18. Prior to the annexation of a part of Johnston on June 1 Tin Top hill near Ladd Observatory on the East Side was the highest point of land in Providence, being 200 feet above sea level. But Neutaconkanut now takes first place, the highest point within the city limits being 255 feet above sea level.
13. "Ladd Observatory". Providence Sunday Journal. June 1, 1890.
14. "A New Observatory Given to Brown". New York Times. October 22, 1891.
15. ^ Bartky, Ian R. (2000). Selling the true time. Stanford University Press. p. 199. ISBN 9780804738743. Retrieved 29 March 2019. Other research-oriented observatories continued to sell time, with varying degrees of financial success.
16. ^ "Time Signals". Providence Journal. December 3, 1893.
17. Fellman, Bruce (March 1992). "Enchanted Evenings: Ladd Observatory Turns 100" (PDF). Brown Alumni Monthly. Retrieved 12 December 2019.
18. ^ "Standard Time". Providence Journal. September 14, 1893.
19. ^ Greer, William (1991). "Aid for the Jewelers and Bankers of Rhode Island". A History of Alarm Security. National Burglar & Fire Alarm Association. pp. 62–63.
20. Upton, Winslow (June 21, 1894). "Report of the Professor of Astronomy and Curator of Ladd Observatory". Annual Report of the President to the Corporation of Brown University. Retrieved 12 December 2019.
21. Treasurer's Report. Brown University. 1906.
22. Treasurer's Report. Brown University. 1916.
23. Upton, Winslow (October 3, 1906). "Report of the Director of the Observatory". Annual Report of the President to the Corporation of Brown University. Retrieved 12 December 2019.
24. "Steward Delaney's New Clock". Brown Daily Herald. Vol. 5, no. 11. September 30, 1895. Retrieved 11 December 2019.
25. Richardson, R.G.D. (October 1914). "Astronomy". Annual Report of the President to the Corporation of Brown University. Retrieved 12 December 2019.
26. "Wireless Plant Being Installed at Brown University". Providence Journal. December 5, 1915. p. 4. Another of the applications to which the plant will be put will be to supply time to the Ladd Observatory from the plant at Arlington, Va., which signals at 10 o'clock every night.
27. Smiley, Charles H. (1935). "Time signals on short-wave radio". Popular Astronomy. 43: 152–157. Bibcode:1935PA.....43..152S.
28. Loveridge, G. Y. (April 17, 1955). "The Cry of Noon: Behind the siren wail each day – stars in their courses, a clock in partial vacuum, and instant electric impulses". The Rhode Islander: Providence Sunday Journal Magazine. pp. 13–14.
29. Mitchell, Martha (1993). "Ladd Observatory". Encyclopedia Brunoniana. Providence, RI: Brown University Library.
30. Loucks, Donovan K. (29 March 2006). "H.P. Lovecraft's Interest in Astronomy". The H.P. Lovecraft Archive. Retrieved 7 January 2016.

External links

• Ladd Observatory blog

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