Astronomical Regulators: Clocks Built to Keep Solar Time

Astronomical regulator clocks have a history with deep roots in the scientific community. These clocks needed to be the most accurate in the world, as they were made to be used with telescopes in observatories to record the exact second a planet or star crossed a transit meridian. Astronomical regulators were meant to measure sidereal time, which means time according to the heavens rather than standard solar time used by us common folk on earth. Solar time is actually less accurate because the earth’s orbit is oval, so by using the stars to tell the time, one can compensate for the elliptical orbit of the earth.

Astronomical regulators often have a built-in thermometer because ambient temperature in the earth’s atmosphere will actually bend the light perceived by the telescope from the star being viewed. The astronomer would then note the time and temperature and be able to compensate for this variation. As you see, the accuracy of an observatory’s regulator is just as important as its transit telescope.

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A 19th century astronomical regulator clock made by Condliff of England.

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E. Howard, and American clock maker, created this astronomical regulator clock.

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Another American clock maker to produce astronomical regulator clocks was the United States Clock Co.

The first observatory in the world, the Observatoire de Paris, was established in 1667 and used a clock made by Abraham Louis Breguet. That was soon followed in 1675 by the Royal Greenwich Observatory in England, where Thomas Tompion was commissioned to build two regulators for the Greenwich observatory, and thus was born the first astronomical regulators.

By the middle of the 18th century, many improvements were made in the design of clock mechanisms, such as temperature compensating pendulums, more accurate escapements and maintaining power (used to keep the clock under constant force while one is in the act of winding the clock). As these improvements were implemented, an observatory would replace their older regulators and update with this newer technology (seem familiar?). Besides Breguet and Tompion, some of the most recognizable names in engineering these precision timekeepers are: Christopher Huygens, who is credited with the first use of pendulum in a clock, and George Graham, as inventor of the deadbeat escapement. Further reading can be found in the series of three books written by horologist Derek Roberts, titled “Precision Pendulum Clocks,” published in 2003-4 by Schiffler books. For anyone seriously interested in astronomical clocks these three books are must reads.

By the beginning of the 19th century, demand for astronomical regulators had grown exponentially, and many well-respected clockmakers began production. Available on the market today are regulators by the English makers Condliff, Dent, Mercer, Frodsham and Molyneux, just to name a few. Several German clock makers produced Astronomical clocks with Strasser & Rohde, Lenzkirch, Junghans and Riefler clocks sometimes found on the market. In America, Seth Thomas, E. Howard, WM. Bond of Boston, United States Clock Co., Chelsea Clock Co., and Chas. Fasoldt are a few U.S. makers who made this type of clock. It seems few French clockmakers made and sold astronomical regulators.

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Astronomical regulators dials display the minute marker with the largest hand, which is pivoted in the dial center, with two smaller dials marking the hours and seconds. These dials are usually placed above and below the center arbor.

The easiest way to recognize an astronomical regulator is by the dial. Usually the dial has a matte silver finish, with the largest hand being the minute marker that is pivoted in the dial center with two smaller dials marking the hours and seconds. These dials are usually placed above and below the center arbor. Precision astronomical regulators often have pendulums with invar steel or gridiron type pendulum rods, sometime with mercury filled jars for temperature compensation. The movements were always heavy duty, with thick brass plates, highly polished precision cut wheels and often with jeweled escapements and bushings.

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Precision astronomical regulators often have pendulums with invar steel or gridiron type pendulum rods, sometime with mercury filled jars for temperature compensation.

Most examples of the finest astronomical regulators are in museums and a few reside with advanced collectors. Even though these clocks have been rendered virtually obsolete with the advent of atomic and quartz technology, a few fine craftsmen are still making special order astronomical regulators today. Prices for astronomical regulators clocks can vary wildly with very modest examples beginning at around $5,000 and quickly escalating to 10, 20 even $50,000. Nowadays, it is not unusual to see auction results just under $200,000 for some of the larger E. Howard floor regulators, and it is not hard to imagine one of the more important early English made astronomical regulators topping several million dollars.

So, if you ever see a clock with this kind of funny looking dial, look twice, as you may be looking at an extremely rare and valuable regulator!