Flamsteed Astronomy Society

Where East meets West” by Graham Dolan

— January 9, 2006

Graham Dolan by Mike Dryland

Graham Dolan — Senior Education Officer ROG/NMM

(Photo: Mike Dryland)


Apologies for the old picture.  At the time of this talk, Graham was sporting a splendid new beard!

Graham Dolan talked to us on the broad subject of the world’s Prime Meridian “Where East meets West”

Graham has spent an extraordinary amount of personal time and money to research this talk which he illustrates with over 800 slides!  He thoroughly covers the history, astronomy, and geography of the Prime Meridian.

Graham began with an introduction to the navigation problem, latitude and longitude, and the historical background — how did the Meridian come to be at Greenwich?  The search for Longitude; the founding of the Observatory in 1676; the work of the Astronomers Royal from Flamsteed to Airy; the development of the Lunar Distance technique; the Nautical Almanac; and the Longitude Conference of 1884 at which the Greenwich Meridian received worldwide recognition.

He gave a rundown on the instruments used at Greenwich to determine the time and thereby position a Meridian from stellar observation (Did you know that Halley’s Transit Instrument, built by the formidable Robert Hooke, was actually sited west of the original building 40 m away from his meridian wall?).  Graham talked about the process of aligning the instruments on a meridian using circumpolar stars, and looked at the history of positioning Azimuth Markers on places visible from the Observatory to assist re-alignment after maintenance etc.  Pond erected a marker in Epping forest almost 11 miles north of the Observatory.  The present laser which shines down the line of the Meridian, reaches to Royston, almost at Cambridge.

Graham showed us a history in pictures of marking the line at the Observatory itself and across the park.  By the 1930s the Meridian was marked on the path north of the Observatory outside its fence.  The marks are still there today.  But the line wasn’t marked in the Courtyard until 1960 when the Observatory was opened to visitors as a museum.  The present courtyard paving was laid in 1967.

The final part of Graham’s presentation was a tour de force survey-in-images of Meridian markers in England, north and south of the Observatory.  Graham has personally visited and photographed dozens if not hundreds, of markers from Tunstall in Lincolnshire to the north, down to Peacehaven Sussex in the south.  The Meridian is marked by trees, obelisks, monuments, sculptures, and a veritable cornucopia of inscriptions on pubs, schools, and dry cleaners.   Graham’s survey-in-pictures is presented at one slide a second to the background ticking of Harrison’s legendary marine timekeepers, H1 to H4.


MRD 11/1/2006


Halley’s Transit Telescope by Robert Hooke 1721  © NMM

The Meridian from Peacehaven to Tunstall © NMM

Read More at —

“On the Line — The story of the Greenwich Meridian” by Graham Dolan; NMM 2003

Greenwich Time and the Longitude” by Derek Howse; various editions OUP and NMM

And lots of information on the web starting at the Observatory’s history on the ROG site

The ROG courtyard and meridian line marking 1967 © NMM

Meridian marker Yorkshire  © NMM

Azimuth marker obelisk in Epping Forest