Ladd Observatory is an astronomical observatory at Brown University in

Providence, Rhode Island Providence is the capital and most populous city of the U.S. state of Rhode Island. One of the oldest cities in New England, it was founded in 1636 by Roger Williams, a Reformed Baptist theologian and religious exile from the Massachusetts ...

. Founded in 1891 it was primarily designed for student instruction and also 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 World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

. 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 A Schmidt camera, also referred to as the Schmidt telescope, is a catadioptric astrophotographic telescope designed to provide wide fields of view with limited aberrations. The design was invented by Bernhard Schmidt in 1930. Some notable e ...

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 A technology museum is a museum devoted to applied science and technological developments. Many museums are both a science museum and a technology museum. Some of the most historically significant technology museums are: *the Musée des Arts ...

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 Neoclassical architecture is an architectural style produced by the Neoclassical movement that began in the mid-18th century in Italy and France. It became one of the most prominent architectural styles in the Western world. The prevailing style ...

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 , .

Telescopes

The primary

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observ ...

is a

refractor A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spyglasses and a ...

with a aperture objective and focal length of . 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 Flint glass is optical glass that has relatively high refractive index and low Abbe number (high dispersion). Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The currently known flint glasses have refractiv ...

by the optical works at Jena in Germany. The equatorial mount and mechanical

clock drive In astronomy, a clock drive (also known as a field rotator) is a motor-controlled mechanism used to move an equatorial mounted telescope along one axis to keep the aim in exact sync with the apparent motion of the fixed stars on the celestial ...

were made by George N. Saegmuller. This telescope was used for scientific work such as lunar

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

timings to make a more precise determination of the orbit of the Moon. Instruments such as a

filar micrometer A filar micrometer is a specialized eyepiece used in astronomical telescopes for astrometry measurements, in microscopes for specimen measurements, and in alignment and surveying telescopes for measuring angles and distances on nearby objects. Th ...

could be attached to the telescope. Another telescope, a

meridian circle The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nadir. These are special purpose telescopes moun ...

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 Ladd provided an accurate regional timekeeping service by transmitting a

time signal A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day. Church bells or voices announcing hours of prayer gave way to automatically operated chimes on public clocks; however, a ...

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 A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a harmonic oscillator: It swings back and forth in a precise time interval dependent on i ...

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

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Prior to the Ladd time service the city relied on time signals from either

Harvard College Observatory The Harvard College Observatory (HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, United St ...

or the

United States Naval Observatory United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the Depo ...

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 A clockmaker is an artisan who makes and/or repairs clocks. Since almost all clocks are now factory-made, most modern clockmakers only repair clocks. Modern clockmakers may be employed by jewellers, antique shops, and places devoted strictly t ...

) who repaired and calibrated watches. The signals were also used to directly control a clock network of several hundred

slave clock In telecommunication and horology, a slave clock is a clock that depends on another clock, the master clock. Modern clocks are synchronized through the Internet or by radio time signals, to Coordinated Universal Time. UTC is based on a network ...

s in various business offices. The revenue that the university received from the time signal service in 1906 was () 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 Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lette ...

between

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and Providence. The signals were transmitted by the Navy radio facility

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. In 1915 Brown installed a sophisticated "wireless plant" consisting of a 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. Hammarlund Comet Pro

Calibration by Naval Observatory time signals from radio station WWV resumed after the war ended. These early transmissions were

longwave In radio, longwave, long wave or long-wave, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band. The term is historic, dating from the e ...

, so called due to the long

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...

. Frequencies, and corresponding wavelengths, from to 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 . 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

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, 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.

References

External links