Essential Information

Royal Observatory
Price Ticketed

Free entry for members. Not a member? Join now

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

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

Royal Observatory

  • Visit the Prime Meridian line
  • See the best view in London
  • Guaranteed entry time
  • Audio guide included
  • Planetarium shows not included

Royal Museums Greenwich Day Pass

  • Save 25% with combo ticket
  • Cutty Sark
  • Royal Observatory
  • Guaranteed entry time
  • Planetarium shows not included

Member tickets

  • Unlimited free entry
  • Priority booking and exclusive events
  • Access using your membership card
Membership card number required

Become a Member

  • Unlimited entry all year
  • Royal Observatory
  • Cutty Sark
  • Planetarium Shows
  • Special exhibitions
Direct Debit One-off
Individual: £50 Individual: £60
Family: from £60 Family: from £70