The Royal Observatory Greenwich celebrates its 350th anniversary in 2025

2025 marks 350 years since the foundation of the Royal Observatory, the first state-funded, purpose-built scientific institution in Britain. 

The Royal Observatory was established by Charles II to make life-saving astronomical observations that could help navigators at sea determine their longitude (east-west position). The Astronomer Royal was initially charged with producing accurate star maps that would help sailors determine their location at sea. 

Despite producing a very accurate star catalogue and chart by the 1720s, the Observatory continued to develop better ways of measuring longitude by the stars. In 1767, the fifth Astronomer Royal began to publish the Nautical Almanac so that sailors could use a sextant to measure longitude by the Moon. Updated each year, this book of astronomical data was generated by a national network of human computers who sent their work to Greenwich.

In parallel, clockmakers tried to create a sea clock that could provide a reference time for longitude at sea. By the 1760s, the English carpenter and clockmaker, John Harrison, had proved that such a timekeeper was feasible and his first four designs are on display in the ‘Time and Longitude’ gallery.

The Royal Observatory Greenwich is now one of the most important scientific sites in the world. Sitting within the Maritime Greenwich UNESCO World Heritage Site, it was adopted as the defining location of the Prime Meridian of the world at the International Meridian Conference in 1884. It is also the home of Greenwich Mean Time (GMT) which was distributed both locally and nationally, via the Time Ball installed in 1833, the signal for Railway Time in 1852 and the time signals (‘BBC six pips’) broadcast from 1924.’

As observing conditions in Greenwich deteriorated, the Royal Observatory eventually moved to Herstmonceux Castle in 1958 and the Greenwich site opened as a museum from 1960. The Great Equatorial Telescope, the largest refracting telescope in Britain, was initially removed from the Observatory, but returned in 1975 as part of the 300th anniversary celebrations. This Victorian telescope is a major attraction for our public observing evenings during the winter.

Today, the Royal Observatory Greenwich is a place of excellent scientific education as well as a museum and home of London’s only planetarium. In 2018, the site became a functional observatory again after a public appeal raised over £170,000, to support the installation of a new, modern telescope for observing the Sun, planets and deep space objects.

 

The key anniversaries in 2025 are: 

  • 4 March 1675 – Charles II appoints John Flamsteed as ‘The King’s Astronomical Observator’, or the first Astronomer Royal 
  • 22 June 1675 – Charles II establishes Royal Observatory 
  • 10 August 1675 – Foundation stone is laid on the site of Greenwich Castle

 

350 years of pioneering research will be celebrated throughout 2025. Events will correspond to important moments in the Observatory’s development, acknowledging the extraordinary astronomers who worked there in the past, as well as the curators and astronomers who work there today. 

The season of events kicks off in March 2025 under the theme of ‘People Stories’. Inspiring stories of iconic women including Alice Everett, Elsie Clack and Mary French will be told in a special talk on 28 March. Researchers from the US and Australia will join Dr Louise Devoy, Senior Curator of the Royal Observatory, to discuss the legacy of the first generation of professional female astronomers at the Royal Observatory and observatories around the world.  

On 29 March, a partial solar eclipse will be live streamed from the Royal Observatory Greenwich. This will start a solar season of activities in April. As part of the season, the life of pioneering nineteenth-century astrophotographer Annie Maunder will be showcased in a special planetarium show on her birthday, 14 April. Starstruck: Sun will explore our closest star and the contributions Annie Maunder made to our understanding and study of the Sun.  

In August, a new planetarium show will demonstrate the night sky when the foundation stone was laid in Greenwich Park.  Visitors will have the opportunity to discover the astronomical sights they can spot for themselves today, and how our knowledge and views of these have evolved over time.

Throughout this landmark year, there will also be special events including live science and stargazing demonstrations, family activities, talks and daily historic tours. 

For more information, visit www.rmg.co.uk/350. 

Notes to Editors

  1. The Royal Observatory Greenwich celebrates its 350th anniversary in 2025. Founded in 1675 by Charles II to solve longitude and improve navigation at sea, it is now one of the most important scientific sites in the world. It is the home of Greenwich Mean Time, the Prime Meridian and the UK’s largest refracting telescope. The Observatory galleries and Peter Harrison Planetarium, London’s only planetarium, help unravel the extraordinary phenomena of time, space and astronomy. 
  2. The Royal Observatory Greenwich is part of Royal Museums Greenwich which also incorporates the National Maritime Museum, the 17th-century Queen’s House and the famous clipper ship, Cutty Sark. This unique collection of museums and heritage buildings form a key part of the Maritime Greenwich UNESCO World Heritage Site and is also a major centre of education and research. The mission of Royal Museums Greenwich is to enrich people’s understanding of the sea, the exploration of space, and Britain’s role in world history. For more information, visit www.rmg.co.uk

For further information or to request press images, please contact:

Victoria Mottram, Royal Museums Greenwich Press Office 
press@rmg.co.uk | 020 8312 6789