The Royal Observatory

Royal Observatory Mistresses, Meridians, Longitude & Time

roceeding south on King William Walk, your through early spring gardens. These same paths were once path is blocked by the gold trimmed St. Mary’s trodden by the footsteps of Edmond Halley (the comet), Gate. To the east is a landscaped promenade fea- Charles Mason (and Dixon), Isaac Newton (falling apples), turing prominently a ship in the bottle, perhaps Christopher Wren (St. Paul’s Cathedral) and any number of ten feet in diameter and twenty-five in length. To surveyors and astronomers and Kings and Queens of the realm. the west is the Greenwich Tavern “The Mature The entire “astronomick” enterprise was begun long Neighbourly Gastric Pub, Please Enjoy Responsibly and before the fabled sinking of the Shovell fleet and the Board of Quietly.” Straight ahead, high on a hill, surrounded by the 183 Longitude. The observatory’s origin might possibly have been acre Greenwich Park sits the Observatory. due to pillow talk, a whisper in the ear or a conversation over Climbing that long steep grade, digesting a breakfast of fried wine. Charles II, the Merrie Monarch, had as a mistress, Louise uncured bacon, eggs, bangers, pork and beans and tomatoes are de Keroualle, later the Duchess of Portsmouth, “the face that five land surveyors: 4 Yanks and 1 Brit. The climb is a culmina- saved a thousand ships.” She related to Charles an exciting story tion, the hajj for these surveyors, the once in a lifetime journey about a fellow Frenchman, Le Sieur de St. Pierre and his work to our Mecca: the Prime Meridian, Longitude and Time. solving the problem of longitude using only the heavens. The Observatory grounds proper, dominated by Flamsteed During Charles’ reign, the Great Plague and Great Fire of House, is a hodge-podge of structures assembled over three London occurred. Seeking diversions, Charles turned to the centuries of time. The contemporary surveyors would spend sciences to complement his investments in nautical enterprises. a number of hours traversing through narrow hallways, up Besides having an acknowledged dozen children and seven and down stairs and along stone pathways in beautiful weather mistresses, Charles greatly expanded the powers of the East

>> By C. Barton Crattie, LS, CFM

Displayed with permission • The American Surveyor • Vol. 10 No. 7 • Copyright 2013 Cheves Media • www.Amerisurv.com Easily visible from the Thames, a custom begun in 1833, the Greenwich time ball is dropped at precisely 1:00 p.m., allowing mariners of long ago to set their chronometers from their ships on the river below. Observatory

Displayed with permission • The American Surveyor • Vol. 10 No. 7 • Copyright 2013 Cheves Media • www.Amerisurv.com quadrants and circles and the zenith sectors are mounted to solid stone walls oriented with the meridian. The stars are mapped and charted based on the precise time of their passing the meridian and by their elevation above the “horizon.” The prime meridian of the world, now illuminated at night by a laser, passes through the eyepiece of George Biddel Airy’s 1851 transit circle. In 1884, the international community met in Washington, DC and agreed to use the Greenwich meridian as the world’s prime meridian. In 1913, France finally adopted the meridian which they referred to as “Paris time diminished by 9 minutes and 21 seconds.” As part of this agreement, it is said that Britain The site of the observatory, high on a hill within the 183 acre Greenwich Park. promised to adopt the metric system. The Brits just didn’t say when. The world chose Airy’s meridian but India Company as well as chartering near the place where the Castle stood, with all of England is mapped using Bradley’s the Hudson’s Bay Company. On March lodging-rooms for our astronomical obser- meridian situated about 8 meters west. 4, 1675 the King named 28 year old vator and assistant . . .” Flamsteed’s first James Bradley became 3rd Astronomer John Flamsteed “Royal Astronomical order of business was that he immediately Royal in 1742. The focal point in Observator.” Shortly thereafter, financed proved the Frenchman incompetent. Bradley’s transit room is the telescope through the sale of spoiled gunpowder, he used to chart more than 3,000 stars work began on Flamsteed’s new home and The Greenwich Meridian and establish the meridian that eventu- observatory. The site was chosen by Wren; A meridian is a line running in a north/ ally served as the basis for the famous a deserted castle with very strong existing south direction through the poles of the Ordnance Survey. foundation stones on high ground away earth’s rotation. There have been numer- from the lights and smoke of London. The ous meridians established for differing Royal Warrant stated in part: “Whereas, purposes over the years. Our country’s in order to the finding out of longitude rectangular system of survey has the of places for perfecting navigation and meridian as a primary element. astronomy, we have resolved to build Astronomers establish meridians to a small observatory within our park at map the heavens. The primary instru- Greenwich, upon the highest ground, at or ments of the observatory, the mural

The main gate of the observatory is guarded by the 24 hour slave clock and the one time British standard for linear measurement. The prime meridian of the world originates within these windows, the three-part Meridian Building.

Displayed with permission • The American Surveyor • Vol. 10 No. 7 • Copyright 2013 Cheves Media • www.Amerisurv.com Flamsteed’s meridian disappeared (from an old English astronomer) passes sea, developing the first isogonic lines. following his death and his wife selling through the observatory. Numeric designa- Unfortunately, declination does not his instruments. Evidence said to be tions increase east and west until both remain stationary. remnants of his 100 foot deep well zenith achieve 180 degrees at the international Tobias Mayer of Gottingen University sector and a portion of a quadrant built date-line. This is an arbitrary system, but in Germany was developing a system by Abraham Sharp are the few remain- one agreed to in 1884. (the one St. Pierre shared) of Lunar ing objects of Flamsteed’s 42 year tenure. Latitude is somewhat easy to determine distances. This system is fairly simple Edmund Halley’s iron quadrant by based on the position of Polaris or the and straight forward. Basically, the Graham (and meridian) is on the west sun at noon. Longitude, not so easy. One moon would be in a certain position in side of the same wall holding Bradley’s factor, known early on was a comparison relation to certain stars at precise times. (later) quadrant. of local times. Any number of solutions Observations and computations weren’t There is yet a 5th meridian at have been proposed over the centuries. that simple and straight forward though. Greenwich (unmarked). WGS84 placed A 1687 pamphlet advocated taking Nevil Maskelyne, the 5th Astronomer the 00 degrees location shown on one’s a wounded dog to sea. At a predeter- Royal as well as Charles Mason GPS receiver about 102.5 meters east of mined time, a timekeeper on shore devoted much of their time observing Airy’s meridian. This is due to adjust- would dip a bandage from the dog into and computing, adding to Mayer’s ments based on the earth’s center and not a powder. The dog at sea would yelp work. Unlike any of his predecessors, its surface. However, the good news is at that precise time and the crew would Maskelyne devoted his efforts solely to that because of the movement of tec- know the time ashore. the original charge of the Royal Warrant. tonic plates, the GPS meridian is moving Edmond Halley, 2nd Royal The end result was the Nautical Almanac, toward Airy’s line about 2.5 cm a year. Observator thought the answer might published in 1766, immediately selling Using a pretty good, but inexpensive lie in magnetism. Halley charted over 10,000 copies. Lunars remained in pocket compass, the American delegation declination on a number of voyages at checked Airy’s meridian. We found that it was fairly accurate, being just about 11-1/4 degrees east of north. Perhaps on With the city of London in the the next trip we’ll check declination. background, one of the observatory courtyards. In the foreground are the Longitude remains of what was once a 40 foot Lines of longitude are converging merid- Herschelian telescope and what is ians going either north or south from the purported to be the filled-in remains equator. As mentioned, “longitude naught” of Flamsteed’s 100 foot deep well zenith sector.

One of John Bird’s quadrants (telescope is missing), this one being in the Octogon Room, designed by Christopher Wren. This quadrant is divided into 90 units as well as 96 units.

Displayed with permission • The American Surveyor • Vol. 10 No. 7 • Copyright 2013 Cheves Media • www.Amerisurv.com Occupying both the eastern and use into the 19th century, well after the western hemispheres, this jolly one hour of time per 15 degrees of longi- advent of a reliable chronometer. group of surveyors experience the tude using GMT for the benchmark was The chronometer. The story of majesty of the Royal observatory. implemented. It’s no coincidence that one John Harrison and the years of clock Left to right: David Holland (Virginia), year later, the Greenwich meridian and design leading to H4 is well known. Chuck Dunlap (Virginia), Rich Leu mean time were agreed to internationally Though Maskelyne directed that the (Iowa), Steve Letchford, the Brit in Washington City. £20,000 Longitude Reward be evenly (Virginia) and Bart Crattie (Georgia). In the 19th century, subscriptions to split between Lunars and time, eventu- Greenwich Mean Time became available ally Harrison received £14,315 with using telegraph lines. Each hour, on Mayer’s widow getting a mere £3000. the hour, the time was broadcast. With For his work on Lunars Charles Mason Time the introduction of intercontinental received £1317. With the longitude problem all but underwater cables, direct and near Back at the courtyard, the lads from conquered, efforts at the Observatory instantaneous communication with the the States were entertained with the turned to improving the quality of clock at Greenwich became possible solution to the longitude by a wonderful chronometers and standardizing time. across the world, ceasing the necessity to performer. Clearly and concisely, Lady The site became a proving ground view the heavens. Vanessa related the story of longitude in for the Admiralty, putting a variety a most interesting way. The mischievous of chronometers through a variety of Behind the Success surveyors brought up sidereal time. Time tests. Charles Darwin’s conveyance, While Flamsteed established that the to change the subject. The Beagle carried an astounding 22 speed of the rotation of the earth was chronometers. constant (not really), Bradley discovered Atop Flamsteed House is the red time aberration of light and nutation and ball. Each day since 1833, the ball has Halley paid to have Newton’s papers been raised partially at 12:55. At two published, the true craftsmen, geniuses minutes before the hour, it is brought and scientists were producing the all the way to the top. At precisely 1:00 remarkable machines that allowed (1300), it is dropped. A ritual that long these unprecedented discoveries. There ago allowed navigators of vessels could be no precise measurements made anchored in the Thames to synchro- consistently without the fruits of the early nize their times. Ha. instrument and clock makers’ labors. When the rails were joined The precision necessary (accuracy was in Utah (1869), the American a given, paramount and unspoken) railroad system had over 70 to derive almanacs and ephemera standard local times. In 1883, from observations evolved as the skill Dowd’s American system of and innovation of the time keeping

Displayed with permission • The American Surveyor • Vol. 10 No. 7 • Copyright 2013 Cheves Media • www.Amerisurv.com Queen’s House, and the Royal Maritime Museum at the foot of the hill, share Greenwich Park with the Royal Observatory.

Flanking the front entrance to the Maritime Museum, this ship in a bottle is large enough that if the stopper were removed, a man could climb inside and do maintenance on the ship.

and sighting devices evolved. Prior to Airy’s telescope. The Ramsden’s engine, Graham and Bird eyepiece of this telescope devised an ingenious method of dividing is the center of the the scales on the quadrant. This involved Prime Meridian of the 96 degrees per quadrant because it’s world, agreed to by the easily divisible by two. A conversion international community chart was then applied. The early clocks in 1884. rivaled Harrison’s timepiece for accuracy. Unfortunately, they were stationary and impractical at sea. Tampion’s (c.1670) clock still keeps up with the hours lunch, in a 400 year old pub, and over mariners and aviators of old lived the and minutes in the Octagon Room glasses of ale and bitters, talk turned to importance of that system perfected of Flamsteed house. The unknown the current subject of utilizing coordinates within that cluster of buildings on that personalities of Greenwich have directly as monumentation in our home country. hill in Greenwich Park high above that impacted the surveyor far more, perhaps, Flamsteed and those that followed River Thames. than any of the works of the star gazers. had developed a system over nearly 3 Reluctantly, it was time to go. The five centuries that the entire world grasped, C. Barton Crattie is a land surveyor surveyors had consumed an enormous creating a truly international community. in Tennessee and Georgia. Visiting amount of sights, memories and knowl- It occurred to me that it seems inevitable London and Paris in March of this edge. The time now was for consuming that we, as surveyors would happily year, he expects more good surveying liver, onions and mash, Sunday pot roast utilize the technology now available to stories to come out of that experience. and maybe some fish and chips. Over benefit the public we serve. Just as the