The Ladd Observatory is an astronomical observatory that is operated by the Department of Physics at Brown University in Providence, Rhode Island. It was dedicated on October 21, 1891. The building was added to the National Register of Historic Places in 2000.
|Location||Providence, Rhode Island, US|
|Altitude||226 feet (69 m)|
|Weather||See the Clear Sky Chart|
|Related media on Wikimedia Commons|
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. Construction began in May 1890 and the building was dedicated on October 21, 1891. The total cost of construction and equipping the facility was $30,000 (equivalent to $836,556 today).
The main telescope is a 12-inch (30 cm) refractor with a lens made by John Brashear following the design of Charles S. Hastings. The equatorial mount and mechanical clock drive were made by George N. Saegmuller.
Besides astronomical research and education, Ladd transmitted a time signal via telegraph wire for decades. Observations of stars using a transit instrument were used to calibrate a precision pendulum clock which was equipped with a mechanism to generate the signals. The signals were first sent on Sept 12, 1893. The observatory sold time to Rhode Island Electric Protective (RIEP), a local fire and burglar alarm company. The signals from Ladd were redistributed by RIEP and were used to control several hundred slave clocks in various business offices. The revenue from the time signal service was $200 (equivalent to $5,003 today) per year. Another telegraph wire connected the observatory to the Fire Department at Providence City Hall which was used to signal the accurate time by fire alarm bells at noon and 8:30 p.m. every day. In 1916 the transit instrument observations were discontinued due to a US government order to dismantle the radio set during World War I. The clocks were instead calibrated using radio time signals from the United States Naval Observatory. The transit observations resumed from 1916 to 1917. Calibration by radio continued after the war ended. Clocks in a number of buildings in Providence were regulated using theses signals late in the 20th century. After determining no one was receiving the time signals, the transmissions were discontinued in 1973.
- Donnelly, Marian Card (Winter 1960). "Astronomical Observatories in New England". Old-Time New England. Society for the Preservation of New England Antiquities. 50 (179): 72–80. Retrieved 7 January 2016.
- "A New Observatory Given to Brown". New York Times. October 22, 1891.
- "National Register Asset Details". The Focus Digital Asset Management System. National Park Service. Retrieved 6 February 2016.
- Arnold N. Robinson & Carla Swanson (June 6, 2000). "National Register of Historic Places Registration Form: Ladd Observatory (including accompanying 5 photos, from 1992)" (pdf). National Park Service.
- Upton, Winslow (December 1891). "The Ladd Observatory". Sidereal Messenger. pp. 502–504. Retrieved March 29, 2019.
- Mitchell, Martha (1993). "Ladd Observatory". Encyclopedia Brunoniana. Providence, RI: Brown University Library.
- Smiley, Charles H. (April 1939). "Ladd Observatory at Brown University". The Sky. American Museum of Natural History. pp. 8–9, 22–23.
- "Time Signals". Providence Jounral. December 3, 1893.
- "Standard Time". Providence Jounral. September 14, 1893.
- Bartky, Ian R. (2000). Selling the true time. Stanford University Press. p. 199. ISBN 9780804738743. Retrieved March 29, 2019.
Other research-oriented observatories continued to sell time...
- 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.
- 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. Providence: P.S. Remington & Co. Retrieved March 29, 2019.
- Treasurer's Report. The Providence Press. June 30, 1913. p. 73.
- Upton, Winslow (October 3, 1906). "Report of the Director of the Observatory". Annual Report of the President to the Corporation of Brown University. Providence: P.S. Remington & Co. Retrieved March 29, 2019.
- Loucks, Donovan K. (29 March 2006). "H.P. Lovecraft's Interest in Astronomy". The H.P. Lovecraft Archive. Retrieved 7 January 2016.