The Royal Observatory in Greenwich (II)

Photography by Carlos Dorce

Photography by Carlos Dorce

The Royal Observatory of Greenwich was commisioned in 1675 by Charles II and the building was completed in the summer of 1676. John Flamsteed (1646-1719) was the first Astronomer Royal so the building was often given the title “Flamsteed House” in reference to its first occupant.

In one of the walls, the observatory has the Sepherd 24-hour Gate Clock which is the earliest electrically driven public clocks. It was installed in 1852 ans the dial always shows Greenwich Mean Time (GMT):

Photography by Carlos Dorce

Photography by Carlos Dorce

In the small plate under the clock (G 1692) is an Ordnance Survey bench mark dating from the 1940s. The height above the sea level has been measured and recorded. There are also the British Imperial Standards of Length which were mounted here some time before 1866.

The observatory is also known as the location of the prime meridian of Greenwich meridian:

Photography by Carlos Dorce

Photography by Carlos Dorce

All the tourist want to have a picture with a foot in each side of the meridian:

Photography by Carlos Dorce

Photography by Carlos Dorce

and there is always a large queue to take a picture next to the meridian line which is graved ion the terrace:

Photography by Carlos Dorce

Photography by Carlos Dorce

Another characteristic thing of the obervatory is the Time Ball. The red time ball on top of Flamsteed House is one of the world’s first visual time signals. It was installed in 1833 to enable navigators on ships in the Thames to check their marine chronometers.

The Time Ball drops daily at 13:00hrs (GMT in winter […]). It is raised halfway up the mast at 12:55hrs as a preparatory signal and to the top 2 minutes before it drops.

Photography by Carlos Dorce

Photography by Carlos Dorce

 Let’s start our visit through the gardens of the observatory where we can imagine the great English astronomers looking at the night sky! Ofcourse we find a sundial: 

Photography by Carlos Dorce

Photography by Carlos Dorce

Sundials are the oldest known device for telling the time. As the Earth rotates and the Sun appears to move accross the sky, the shadow cast on the scale indicates the time of the day.

This dial constructed in 1968, represents a globe made from a series of rings. The rings are called ‘armillae’ in Latin, so it is called an armillary dial. The hour scale is on the northern half of the ring representing the equator.

There is also the well where Flamsteed 100-foot telescope was located:

Photography by Carlos Dorce

Photography by Carlos Dorce

Flamsteed used a 30,5 m. well on this site to accomodate a very long telescope:

ROG09

The astronomer sat at the bottom of the well and observed stars that passed directly overhead. It was hoped that placing the telescope in the well would make it possible to create a steady long-focus instrument for very fine measurements. Flamsteed made a few observations from here in 1679, but the damp underground conditions soon made the telescope impossible to use.

A remaining section of a 12 m. reflecting telescope built for the astronomer William Herschel is also in the gardens:

Photography by Carlos Dorce

Photography by Carlos Dorce

The telescope was the largest in the world and cost over 4.000 pounds, paid for by King George III. Completed in 1789 and erected at Herschel’s home near Slough, about 30 miles (48 km) west of Greenwich, it soon became a tourist attraction. Some people likened it to the Colossus of Rhodes, and it was even marked on the 1830 Ordnance Survey map of the area.

Sadly, the Herschels did not use the great telescope for much serious astronomy since it was difficult to set up and mantain. William’s son had it dismantled in 1840. Most of the tube was destroyed when a tree fell on it 30 years later.

On the walls of Flamsteed House is marked  the Bradley Merdian which was the first British National Meridian. The Greenwich meridian was set according to the location of the telescope used by the Astronomer Royal to establish the time. So the Greenwich meridian was in the graved line when James Bradley, the 3rd Astronomer Royal between 1742 and 1762 was in the observatory. When the Airy Transit Circle Telescope was erected in 1850, the Greenwich Meridian was moved approximately 19 feet east to its present location.

Before visiting Flamsteed House there is still time for look at the Dolphin Sundial designed by Christopher St. J. H. Daniel and commisioned by the National Maritime Museum in 1977:

Photography by Carlos Dorce

Photography by Carlos Dorce

So let’s go now to Flamsteed House!

LocationGreenwich Observatory (map)

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One response

  1. […] a few seconds after a long journey, a lot of sea ports decided to have a time-ball (as we saw in Greenwich!) installed on a tower or a […]

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