A Tour of the Royal Observatory Greenwich

This article will cover a tour of my local observatory the famous Royal Observatory Greenwich, however while the observatory has a lot to do with clocks, navigation, latitude and longitude this tour will be focusing on the astronomical aspects of the observatory as that is what this blog is about. This was a professional observatory unlike the community observatory COSMOS observatory on the Isles of Scilly.

The observatory entrance has several interesting astronomical objects. One of them is Flamsteed's Well Telescope, which I find particularly fascinating. It was the first telescope built for observatory back in 1676.

Considering that today we often build telescopes in space or on mountains, I find the idea of building one in a well fascinating. Only a round brick circle remains to indicate the size of the well telescope, but the exact location is unknown since it has been filled in. The purpose of the well telescope was to establish if a star in Draconis had any parallax. Unfortunately, it was the least successful of the Greenwich Zenith telescopes. Due to the depth of the telescope being approximately 30 meters, the telescope suffered from damp. This caused it to be abandoned as the damp effected the plumb line, used to define the zenith in astronomical calculations.

The Herschel telescope outside of the observatory entrance is another fascinating astronomical artefact. This telescope was the world's largest for 50 years after it was finished in 1789. Although looking at it you will be forgiven for thinking that it is not in fact that big. This is because the original telescope was destroyed by a falling tree that is in fact originally 40 feet long and was a local tourist attraction where it is was based in Slough, Berkshire. Unfortunately, this remaining 10-foot-long section is all the remains of the once 40-foot-long telescope 

The telescope itself was actually a special design the Herschelian type this is where the secondary mirror typically found in a reflecting telescope is removed and the primary mirror reflects the light out slightly outside of the tube where it is then focused.

Known for its exceptionally bright images, this telescope may have been instrumental in discovering Enceladus and Mimas, Saturn's sixth and seventh moons.

As soon as you enter Greenwich Observatory, you will encounter Flamsteed House, the original part of the observatory built in 1675. As a matter of fact, it was chosen because of its clear skies, good horizon views, and rural location in 1676! Now its in the centre of London, shortly after the observatory was constructed observations began in the Octagon room.

When John Flamsteed arrived at the observatory there were no telescopes or clocks available. So he had to supply his own with the help of his patron, who also provided some highly accurate clocks with extra-long pendulums that only needed to be wound once a year, which was unusual in those days. As most had to be wound every eight days. The extra-long pendulums are hidden behind the wooden panelling of the Octagon room. As the Octagon room was not aligned with the local meridian, it was not used when building a new star catalogue. Although he did use it for specific events such as observing comets and eclipses.

Next, is the Meridian Observatory, which is somewhat strange for modern astronomers as it is essentially a telescope that measures the height of a star above the horizon as it passes the North/South or Meridian line. Over 600 thousand observations were made at the Meridian Observatory and because of this improved mapping of the stars. These measurements were further improved with the airy transit circle. When the star transited the meridian, the astronomer pressed a switch that caused a needle to puncture paper that rotated on a drum in time with a synchronized clock. Another astronomer would then read the details of the observation.

A major point of interest at Greenwich Observatory is the Large Equatorial Telescope, the eighth largest refractor telescope in the world. to get into it you need to climb some stairs and then walk on a narrow path to get into the actual dome. This telescope is called the Great Equatorial Telescope because the mount is an equatorial mount, used from 1893 to 1947 for observing double stars and spectroscopy. After which London's smog became too great to carry on observing. Despite measuring Jupiter's diameter and viewing comets and many binary stars, the telescope is not renowned for any particular discoveries.

To see what the observatory looks like, why don’t you watch the episode below?

I get commissions for purchases made through affiliate links in this article.