Behind the scenes as Greenwich's planetarium prepares to close for two years

Times

2 days ago

They like to be precise about time in Greenwich. When the Royal Observatory marked its 350th anniversary on Sunday the celebration began — at the third stroke, to use the old time-signal formulation — at 3.14pm, this being the moment when John Flamsteed, the first Astronomer Royal, laid the foundation stone on August 10, 1675.
Twenty-five hours and 16 minutes later, give or take a few pips, my son and I were seated in the observatory's planetarium, tipped well back as if we were at the dentist's, to look upon the same heavens that Flamsteed had been given a royal warrant to chart. At 4.30pm every day throughout August, save Thursdays, the planetarium is presenting a half-hour demonstration of what the night sky looked like on that day in 1675.
Or rather what they understood it to be then, for 350 years is just a blink of an eye in cosmology and little has changed. Not all the 88 constellations recognised today had been identified by Flamsteed's time but Imo Bell, one of ten full-time astronomers at the observatory, picked out some that were known in the 17th century once the glare from modern light pollution was removed from the sky and — to an audible cry of 'woah' from many children in the theatre and perhaps a few adults — hundreds of dots of light and smears of celestial milk suddenly appeared above them on the dome.
The stick diagrams linking the stars were then overlaid with the drawings of mythical creatures and ancient heroes that had been produced for Flamsteed's posthumous Atlas Coelestis by James Thornhill, whose most admired work is the ceiling of the Painted Hall at the Royal Naval College at the foot of the hill. It was a fascinating show with the added benefit on a 34C day of being, as Bell noted, held in 'the coldest room in London', needed to cool the planetarium's four large computers as much as the audience.
The Royal Observatory, Britain's first state-funded scientific institution, was created with the objective of 'perfecting the art of navigation' by producing better star charts. Getting one over the French was an added goal. Eight years earlier, Louis XIV had opened an observatory in Paris, whose first task was to re-survey the outline of France using longitude measurements based on observations of Jupiter's moons. This led the Sun King to remark that he had lost more land to his astronomers than to his enemies.
After the Royal Society had considered sites in Hyde Park and Chelsea, they settled on the castle ruins at the top of Greenwich Park, where the avenues of sweet chestnuts that we see today were still mere saplings. Christopher Wren was asked to divert some of his attention from the creation of St Paul's Cathedral to design an observatory, which progressed with remarkable speed: from the architect being appointed, to Flamsteed moving in and making his first observation took barely 11 months.
Wren's commission was to design a building 'for the observator's habitation and a little for pomp'. A square house, later extended for Astronomers Royal who brought their families, was topped with an octagonal observation room with tall windows, the Camera Stellata. Other observatories were later added, including the fine orange-brick 1895 Altazimuth Pavilion, built to scan the sun, moon and planets with a new telescope.
Perhaps the most famous addition, even more than the green laser that has shot out at nightfall since 1999 to mark the northerly course of the prime meridian, is the large red ball that since 1833 has risen up a mast on top of Flamsteed House from 12.55pm and dropped at precisely 1pm to allow mariners on the Thames to check their chronometers. Today, it is controlled by GPS satellites. If you look closely, the ball has dimples on its surface caused by workmen playing football with it during restoration work in 1959.
By then, Greenwich was no longer a working observatory. Light pollution from electric street lamps and the effects of industry, with vibrations and smoke from the riverside power station down the hill, had an impact on the site's effectiveness, and in 1948 the Royal Observatory left Greenwich for Herstmonceux in East Sussex and then, in the 1990s, for Cambridge. The buildings were gradually opened to the public under the responsibility of the National Maritime Museum and attract more than 700,000 visitors a year.
In 2018, however, research was again conducted in Greenwich, when the computerised Annie Maunder Astrographic Telescope, named after a pioneer who had worked at the observatory in the 1890s, was installed in the Altazimuth Pavilion. This tribute to women stargazers was followed two weeks ago by the appointment of Michele Dougherty as the first female Astronomer Royal, a post that these days is an honorary one but nonetheless important as the science's most public ambassador.
Further development of the site will begin next month when the planetarium is closed for two years, and other buildings in sequence, for a project called First Light. This will create a new entrance pavilion, garden walkway and 'astronomers' court' (a space for interactive experiments and STEM learning), as well as improved access to the Great Equatorial Telescope, which is currently up a winding Victorian iron stair.
Seven refurbished galleries and four new ones will also allow a better show to some of its treasures, 100 of which have been selected by the curator, Louise Devoy, for a forthcoming book called A History in Objects. They include such oddities as the silk and wool observing suit that Nevil Maskelyne, the fifth Astronomer Royal, created in the 1760s to keep himself warm while stargazing on cold nights; a celestial alarm clock designed by Thomas Taylor in about 1827 so that astronomers could wake at the correct time to record a transit; and the 'spider forks' that captured arachnid threads used as orientation lines on the lens (the 1864 observatory inventory lists 'box of cobwebs').
Times are changing at the Royal Observatory and not just twice-yearly, when BST usurps GMT and vice versa. But one thing will remain constant and will surely be enhanced by the redevelopment: the gasps of wonder as a roomful of children have their eyes opened to the star-spangled heavens and they realise the limitless expanse of space.