Essential Information

Royal Observatory
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Incredible technology meets beautiful craftsmanship, visit the clocks that changed the world. John Harrison's marine timekeepers are arguably the most important ever made. 

  • Visit H1, H2, H3 and H4, developed and constructed over John Harrison's life time. 
  • Learn about John Harrison, the man behind the watches. 
  • Discover why the clocks are so important and how Harrison built and tested them.  



What are the Harrison clocks? 

The Harrison clocks were revolutionary in their ability to allow ships to determine their longitude at sea. This development drastically reduced the risk of ships and their crews, along with their precious cargoes, being lost at sea. The Harrison clocks were able to keep time at sea, allowing sailors and mariners to determine their longitude. It took John Harrison most of his lifetime to arrive at the design for H4, which was to be his most successful watch. 

The clocks compensate for changes in temperature and, thanks to extensive anti-friction devices, run without any lubrication.

When Harrison unveiled H1 in 1735 it was the toast of London. Alongside the other Harrison clocks, it is one of the great milestones in clock-making history.

Find out more about John Harrison's ground-breaking timekeepers

Man and woman looking at Harrison's clocks

Learn more in the Time and Longitude gallery

The Time and Longitude gallery tells the story of the quest to find longitude at sea in the age before satellite navigation.

Choose your tickets

A father and son play on the Prime Meridian Line outside the historic Flamsteed House building of the Royal Observatory

Royal Observatory

  • Guaranteed entry time
  • Audio guide included
  • Planetarium shows not included
Adult £16
Child £8
A brother and sister with their back to the camera look out from the viewpoint at the top of Greenwich Park towards historic Greenwich

Royal Museums Greenwich Day Pass

  • Cutty Sark
  • Royal Observatory
  • Guaranteed entry time
  • Planetarium shows not included
Adult £25
Child £12.50

Member tickets

  • Free Museums entry
  • Priority booking
  • Membership card number required
Advance booking recommended
National Maritime Museum

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  • Royal Observatory
  • Cutty Sark
  • Planetarium Shows
  • Special exhibitions
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Family: from £65 Family: from £75