Aug 102013


The Royal Observatory in Greenwich (now a borough of London), was commissioned in 1675 by King Charles II. The foundation stone was laid on 10 August. At that time the king also created the position of Astronomer Royal, to serve as the director of the observatory and to “apply himself with the most exact care and diligence to the rectifying of the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting of the art of navigation.” He appointed John Flamsteed as the first AR. The building was completed in the summer of 1676.

There had been significant buildings on this land since the reign of William I. Greenwich Palace, near the site of the present-day Maritime Museum, was the birthplace of Henry VIII, and was apparently a favorite place for the king to house his mistresses, so that he could easily travel from his palace in Whitehall to see them.


The establishment of a Royal Observatory was proposed in 1674 by Sir Jonas Moore who, in his role as Surveyor General at the Ordnance Office, persuaded King Charles II to create the observatory. The Ordnance Office was given responsibility for building the observatory, with Moore providing the key instruments and equipment at his own personal cost. Flamsteed House, the original part of the Observatory, was designed by Sir Christopher Wren, probably with the assistance of Robert Hooke (post 18 July), and was the first purpose-built scientific research facility in Britain. It was built at a cost of £520 (£20 over budget) out of largely recycled materials on the foundations of Duke Humphrey’s Tower, which resulted in the alignment being 13 degrees away from true North, somewhat to Flamsteed’s chagrin.

The original observatory at first housed the scientific instruments to be used by Flamsteed in his work on stellar tables, and over time also incorporated a number of additional responsibilities such marking the official time of day, and housing the Nautical Almanac Office. Moore donated two clocks, built by Thomas Tompion, which were installed in the 20 foot high Octagon Room, the principal room of the building. They were of unusual design, each with a pendulum 13 feet (3.96 metres) in length mounted above the clock face, giving a period of four seconds and an accuracy, then unparalleled, of ± 7 seconds per day.

Tompion Astrolabe Clock

Tompion Astrolabe Clock

Four separate meridians have been drawn through the building.  The Prime Meridian, basis of longitude, was established in 1851 and adopted at an international conference in 1884. It passes through the Airy transit circle of the observatory. It was long marked by a brass strip in the courtyard, now upgraded to stainless steel. How many people have had their photographs taken straddling the Prime Meridian over the years?


Since 16 December 1999 the Prime Meridian has been marked by a powerful green laser shining north across the London night sky.


Modern geodetic reference systems, such as the World Geodetic System and the International Terrestrial Reference Frame, use geographical coordinates based on the physical center of the earth and not the surface markers the older Greenwich systems used. The Prime Meridian of these modern reference systems is 102.5 metres east of the Greenwich astronomical meridian represented by the stainless steel strip. Thus the strip is now 5.31 arcseconds West.

Greenwich Mean Time (GMT) was until 1954 based on celestial observations made at Greenwich. Thereafter, GMT was calculated from observations made at other observatories. GMT is more properly called Universal Time at present, and is calculated from observations of extra-galactic radio sources. To help others synchronize their clocks to GMT, AR John Pond had a time ball installed atop the observatory in 1833. It still drops daily to mark the exact moment of 1 pm (13:00) year-round (GMT during winter and BST during summer)

The Ball Has Dropped

The Ball Has Dropped

The scientific equipment was gradually moved out of the observatory to other locations over the course of the 20th century, starting in 1924. Today the buildings include a museum of astronomical and navigational tools, which is part of the National Maritime Museum, notably including John Harrison’s prize-winning longitude marine chronometer, H4, and its three predecessors. Several additional horological artefacts are displayed, documenting the history of precision timekeeping for navigational and astronomical purposes, including the mid-20th-century Russian-made F.M. Fedchenko clock (the most accurate pendulum clock ever built in multiple copies). It also houses the 28-inch Grubb refracting telescope of 1893, the largest of its kind in the UK. The Shepherd Clock outside the observatory gate is an early example of an electric slave clock.

The Shepherd Clock

The Shepherd Clock

The Harrison Chronometer

The Harrison Chronometer


One of the most famous Greenwich watch makers was John Forrest (no relation), active from 1857 to 1911, and chronometer maker to the Admiralty for several years. My John Forrest pocket watch is a prized possession, although I have never been able to find a watchmaker to work on the delicate fusee movement (employing  a chain and conical pulley for greater accuracy than cog wheels).

John Forrest chronometer

John Forrest chronometer

The one time I visited Greenwich observatory I was impressed by a giant fig tree growing near the wall of the main building entwined in an external staircase. I don’t know if it ever fruited.  Nothing compares to biting into a freshly picked fig.  But they do well in desserts and preserves.  Fig preserve is a common pastry filling here in Argentina.  Here is a favorite dessert recipe of mine. The dark chocolate and mascarpone in the topping are essential.  The fruits and nuts can be varied or omitted according to taste. You can also add a little icing sugar to the mascarpone if you want a sweeter topping.


Caramelized Figs with Chocolate Mascarpone 


6 ripe figs

1 ½ cups (360g) mascarpone

2 oz (60g) dark chocolate, shaved

2 tbsps finely chopped dried fruit (apricots, apples, mango, or papaya)

2 tbsps coarsely chopped pistachio nuts

1 ½  tbsps honey, plus extra for plating


Preheat broiler grill on high.

Combine mascarpone, chocolate, dried fruit, and pistachio in a bowl.

Cut each fig in half and place, cut-side up, on a baking tray. Drizzle ½ teaspoon of honey over each fig half.

Broil the figs for 2-3 minutes or until slightly caramelized.

Divide the figs among 6 serving plates and top with the mascarpone mixture. Drizzle over a little extra honey.

Serves 6