|Norman Lockyer Observatory|
Salcombe Hill, Sidmouth
The Kensington Dome
(The clock-weights drive the telescope tracking motor)
At 7.15pm on Wednesday 13th March 2013 - when it was much darker than shown in this photo! - a group of ten Open University Graduates gathered for a tour of the Norman Lockyer Observatory at Salcombe Hill above Sidmouth.
Despite occasional showers, the sky was generally very clear. As a result, the temperature on top of the hill was bitterly cold. Everyone had come wrapped up warmly, and some even had the foresight to bring torches. There is special 'red' lighting on the site, which is intended not to interfere with observers' night vision. However, it doesn't help much with normal vision, and it was quite easy to stray off the paths.
The first thing to see was the observatory's subject matter - the night sky. Looking south from the main building, Jupiter was clearly visible in the constellation of Taurus - or rather, in line with Taurus. The Earth was on the opposite side of the Sun from Jupiter in March, and our line of sight to the Sun pointed towards the constellation Aries. (Of course it did - it was March!).
As the Sun was slowly obscured by the Earth's horizon, so was Aries, but Taurus became visible near the horizon as darkness fell. There was Jupiter behind the Sun - and six times as far away - in line with Taurus. We measure planetary distances in terms of our distance from the sun (150 million kilometers). The distance to Jupiter was therefore about six 'astronomical units' (nearly one billion kilometres).
|Aldebaran is big|
The other stars of Taurus (those which are visible to the naked eye) are at even greater distances. The most distant is 'Tien Kwan' ('Heaven's Gate' - at the tip of Taurus' right horn, which marks the Chinese celestial asterism, 'Net'). Tien Kwan is 440 light years away - thirty million astronomical units - four million billion kilometres!
Aldebaran is a red giant star about twice the mass of our Sun. It was once like our Sun - the temperature and density of the hydrogen in the core making nuclear fusion possible. The fusion generates high energy radiation which, apart from providing the heat and light of the star, prevents the core from collapsing. However, the nuclear fusion converts hydrogen into helium - decreasing the density of hydrogen. Eventually the fusion slows until it doesn't generate enough radiation to support the core - and the core collapses.
But the collapse generates heat! The core became so hot it made the rest of the star expand. Aldebaran is now 44 times the radius of the sun - with a surface area two thousand times as great. Although it is giving out five hundred times the energy of the sun, it's surface temperature is lower (only 4,000K compared with the Sun's 6,000K). The low temperature is the reason for the 'red' colour.
Tien Kwan is actually two stars orbiting very close together (at a separation of about one astronomical unit!). The smaller star is about the mass of our Sun, and swamped by the light of the bigger star - a blue giant. This has about 11 times the mass of the Sun. The increased mass means more energy at the core, and faster fusion. Tien Kwan is about ten times the radius of the Sun (one hundred times the surface area), but still hotter at the surface - it glows blue where Aldebaran is red. Because of it's rapid energy production, Tien Kwan will collapse at the core in a much shorter time that the sun (millions rather than billions of years).
|Betelgeuse is even bigger|
(For comparison - Rigel is almost as big as Aldebaran)
There had already been enough to see to keep an astronomy student going for a year - and the telescopes were yet to come! In the hundred yards from the main building to the 'Kensington' dome it had been possible to contemplate almost inconceivable times and distances.
The Kensington Dome offers a journey back in time - a journey of about a century. There was the beautiful telescope which Norman Lockyer had used for his solar observations at the Kensington Solar Physics Observatory. In order to observe the Sun, Lockyer set up his telescope to project the Sun's image onto a screen - or through a spectroscope. It was by using spectroscopy that he discovered a previously unknown element in the Sun's outer layers - helium.
This helium is not thought to be the product of nuclear fusion at the Sun's core. The current model, based on the observed expansion of the universe, is that, shortly after a 'big bang', protons and neutrons formed. Within the first minutes of the Universe's existence, The neutrons combined with some of the protons to form 'alpha particles' (helium nuclei). About a quarter of the total number of nuclei that resulted were helium. (The rest were hydrogen - and about 1% lithium.) After nearly 400,000 years the nuclei picked up electrons and became atoms, which have existed unchanged ever since - for more than thirteen billion years. As a result, about a quarter of the Sun's mass is made up of these primordial helium atoms.
|Kensington Telescope on its|
compensatory equatorial mounting
Initially the image just seemed to be a white disc. As the eye adjusted, the familiar bands and great red spot became visible. The clarity of the image would vary with the turbulence in the atmosphere. However, the planet remained dead-centre in the field of view. This was because Vic had set the clockwork motor running, which makes the telescope rotate on its mounting at the same rate as the Earth - but in the opposite direction. This is very convenient, but does mean the eye-piece may move out of reach during observation. To solve this problem the dome has an essential extra piece of equipment - a stepladder.
|Jupiter and the Galilean Moons|
|The McClean Telescope|
set up for solar observation
The telescope was made in Dublin by Sir Howard Grubb in 1894. This is the same model as the one used for the International Astrographic Survey of 1896. With an eye for a bargain Frank McClean had ordered a second identical telescope - special offer, half price. After his father's death, Francis gave one to Norman Lockyer, and one to the Radcliffe Pretoria Observatory in South Africa.
|Fireball over Chebarkul 15th February 2013|
Fragments of the meteoroid (called 'meteorites' once they hit the ground) have been found. The heaviest piece so far found weighs about two kilogrammes. Professor Viktor Grokhovsky, of the Institute of Physics and Technology, at the Ural Federal University, has led a team who analysed the fragments and estimate that the original meteoroid was about seventeen metres across and weighed about ten thousand tonnes.
|2kg fragment of the Chebarkul meteorite|
|An iron meteorite -|
cut to show the metal structure
Professor Peter Brown of the 'Western Meteor Physics Group' at the University of Western Ontario (London, Ontario) has analysed atmospheric data collected during the fall. He concurs with Grokhovsky's estimate of the meteoroid's size, and calculates that it originated in the 'Asteroid Belt' - a ring of rocky and iron debris orbiting between the orbits of Mars and Jupiter.
|SPAM collates meteor data|
by detector and amplitude
Time is represented by the diagonal direction from top left to bottom right - so the bottom right surface represents the present moment. The two axes of the front slice are initially confusing. Frequency is represented horizontally - different countries use different radar frequencies to detect meteors. The vertical axis represents amplitude - the strength of the 'echo' from the meteoroid, which gives an indication of its size.
Longer traces imply less transient objects - including aircraft. There is a continuous trace representing the moon. Spikes result from meteor impacts. As one watches, a series of spikes appear, some much larger than the others. David explained that these meteors were created by small particles - little more than dust grains. Their velocity relative to the Earth may be very high. In extreme cases, when they are travelling in the opposite direction to the Earth, their relative velocity could be up to seventy kilometres per second straight towards us.
|The 'Perseids' meteor shower in July|
At certain times of the year the Earth passes through the orbital path of comets. Each orbit is strewn with material boiled off the comet by the Sun. The Earth ploughs into each cometary orbit in the same direction each year - heading directly towards the same constellation in the sky. In July, for example, the Earth is moving directly towards the constellation of Perseus when it crosses the path of comet Swift-Tuttle. The resulting meteors all appear to originate in Perseus and radiate outwards in all directions. These meteors are called 'Perseids', after the children of Perseus and Andromeda in Greek mythology.
|A time exposure of the Andromeda Galaxy|
|The 'Local Group' of galaxies|
relative sizes and positions
M31 = Andromeda,
M33 = Triangulum
From the cold and exciting darkness of the Salcombe hilltop, with its wealth of fascinating astronomical opportunities, the intrepid group returned to the warmth and brightness of the Donald Barber Lecture Theatre in the main building. Raising its own funds, the Society built this facility in 2006, in memory of Donald Barber, who was Director of the Observatory from 1936 to 1963.
|Donald Barber Lecture Theatre|
Needless to say, Alan concentrated on the Observers Group. (There are an Adult Observers Group, and a Young Observers Group.) Observers are divided between 'Astronomy' and 'Solar, Planetary & Meteor', according to what they want to study. However, all meet together every Friday at 7.30pm. There are enough small astronomical telescopes for everyone to set up outside and have fun observing the universe.
|"What's that light in the sky?"|
Every month there is a Society Lecture in the Donald Barber Lecture Theatre - usually on a Monday night. There are also open days, astronomy courses open to the public, and special astronomy days - either to do with astronomy generally, or at any time when there is a significant astronomical event in the night (or daytime) sky.
|The 2012 Transit of Venus|
recorded safely through clouds
by Melbourne film-maker
Canon EOS 60D
There are only two transits each century, eight years apart. The transit in 2012 was sadly when the Sun was not visible from Salcombe - making the 2004 event unique for this generation in Devon.
Wednesday 13th March was a truly glorious evening out for the Open University Graduates.
Many thanks to Ann Reed for arranging the visit
- and to Vic Papai, David Strange, and Alan Green for such a memorable event.
To find out more about the Norman Lockyer Observatory Society, and maybe get involved, contact:
01395 579941 (not always staffed!)
or take a look at the Norman Lockyer Observatory Society website: