Partial eclipse of the Sun
There will be a partial eclipse of the Sun during the afternoon of Saturday 12th October. As viewed from the UK, about half the area of the Sun will be covered by the Moon at mid-eclipse, making it the best solar eclipse for observers in the UK since 1961.
Full details of the time of the eclipse at various locations in the UK, and instructions on how to observe the eclipse safely, feature on a leaflet, which has been sponsored by several astronomical organizations in the UK. (Text of leaflet appears at the end of this notice.)
On this occasion, no total eclipse will be seen from anywhere on the Earth. Maximum coverage of the Sun will be 76% for any viewers located in the Arctic region.
Eclipses of the Sun occur when the Moon passes directly between the Earth and the Sun, so they take place only at New Moon. Because of the way the Moon moves around the Earth and the Earth around the Sun, solar eclipses do not happen every month. There are between two and five every year, but each one is visible only in the limited band across the Earth's surface where the Moon's shadow happens to fall - which is different every time. At any particular place on Earth, solar eclipses are not so frequent.
The last solar eclipse visible from the UK was a partial one on 10th May 1994. The next one will be on 11th August 1999, when the eclipse will be total over part of the southwest of the UK. The last total solar eclipse visible from the mainland of the UK was on 29th June 1927. (One in 1954 was total from the northernmost of the Shetland Islands.) The next after 1999 will be in 2090. Other total eclipses of the Sun take place on 9th March 1997 (visible from Siberia and the Arctic) and on 26th February 1998 (visible on a track from the Pacific to the Atlantic oceans, crossing the north coast of South America).
A partial solar eclipse is a fascinating natural phenomenon, but is not of any practical scientific use, unlike a total eclipse which provides a special opportunity for studying the solar corona - the tenuous layers of hot gas around the Sun which are much fainter than the familiar yellow disk.
Contacts for further information:Dr Jacqueline Mitton (RAS Public Relations Officer) Phone: 01223 564914 E-mail: jmitton @ast.cam.ac.uk
Dr Yvonne Elsworth (Solar Physicist, Birmingham University) Phone: 0121-414-4597
Prof. Douglas Gough (Solar Physicist, Cambridge University) Phone: 01223 337518
Eclipse information on the World Wide WebEclipse Home Page of Fred Espenak at the Goddard Space Flight Center: http://planets.gsfc.nasa.gov/eclipse/eclipse.html
HM Nautical Almanac Office: http://www.ast.cam.ac.uk/~nao/eclipse.html
On the afternoon of Saturday October 12 over half the Sun will be covered by the Moon in the best solar eclipse visible from the UK since 1961. The table gives timings for various locations.
Solar eclipses occur when the Moon passes in front of the Sun. If we were out in space we would see the Moon's shadow falling on the Earth. People within the Moon's shadow experience a solar eclipse, which is total in the central part of the shadow, and partial in the outer regions. On this occasion, no total eclipse will be seen from anywhere because the central part of the Moon's shadow misses the Earth.
Each year at least two solar eclipses occur, and sometimes as many as five, although not all can be seen from any one place. Total eclipses, in particular, are rare from a given place on Earth. A total eclipse of the Sun will be visible from the UK on 11 August 1999, but you will have to be in Cornwall, Devon or Alderney to see it as total.
The partial eclipse on October 12 will begin shortly before 2 pm BST when the Moon takes a small bite out of the top right of the Sun's disk (see diagram). This bite will gradually grow larger until, shortly 3 pm, the top half of the Sun will be covered. Then the Moon will move away again. The whole eclipse will last about two and a half hours.
Surprisingly, even at mid eclipse it won't seem any darker than normal because your eyes will adjust to the reduction in sunlight, nor is it likely to feel any cooler. Most people won't even notice that an eclipse is underway unless they are told.
Observing the eclipse
Extreme care must be taken when observing the eclipse, because of the blinding brilliance of the Sun. Never, ever look directly at the Sun through binoculars or a telescope, for you will risk permanent eye damage. Even staring at the Sun is dangerous, and sunglasses are no protection. Hospitals regularly see patients who have damaged their eyes while watching eclipses. Don't be among them!
The best and safest way to observe the Sun is to project its image onto a light-coloured surface with binoculars or telescope. This has the added advantage that a group of people can watch at once. Clamp the instrument firmly on a tripod or, if you have binoculars, simply hand-hold them. Put a cap over the finder scope (the small sighting scope on the side of the main telescope tube) or the other half of the binoculars to prevent accidents.
Align the telescope towards the Sun by using its own shadow cast on the screen as a guide (don't look through it!). Adjust the distance between the eyepiece and screen to give a satisfactory image size - perhaps 6 inches or so across - and focus the telescope until the edge of the Sun's image is sharp. You will notice a slight 'boiling' of the image caused by air currents, like looking through a heat haze.
If you are using a reflector larger than about 4 inches (100 mm) aperture, stop it down to prevent heat damage to the secondary mirror and eyepiece. Do so by taping a cardboard disk over the front of the tube, with a hole about 3 inches wide cut in it. Offset the hole from the centre for best images.
While watching the eclipse you may see some dark sunspots, which are cooler patches on the Sun's surface. They will appear brownish by comparison with the jet-black lunar silhouette. Note also the jagged edge of the mountainous Moon as it progresses across the face of the Sun.
No telescope? Try projecting an image onto a screen with a pinhole camera. Pierce a pinhole in a piece of cardboard or stiff paper and hold it up to a window facing the Sun. Pull the curtains to darken the room and place a white screen or sheet of paper a few feet inside. An image of the Sun will fall on the screen - small and faint, but clearly non-circular as the eclipse progresses. Experiment beforehand to find the best combination of pinhole size and projection distance.
If you are outdoors, look at the ground in the shade of a tree - it is often covered with small images of the Sun, for the gaps between the leaves act like pinhole cameras and each one projects its own image of the partially eclipsed Sun.
For naked-eye observing you can look through a welder's glass (no. 14 or higher), or a filter specially produced for observing the Sun made of Mylar, a metal-coated plastic film. Colour film or some modern types of black-and-white film are not safe as filters. This is because eye damage is caused predominantly by infrared (heat) rays, which are not blocked by the dyes in colour or certain black-and-white films. Older types of black-and-white film use silver granules, which do block infrared, and a couple of densely exposed layers of this type of film can be used for brief glimpses, with care.
Location Start of Middle of End of Maximum area
How the eclipse will look in its early, middle and late stages
None of the sponsoring organizations, nor anyone involved with the production of or distribution of this information shall be liable for damages arising from the use of this information.
Published by National Astronomy Week, c/o Jodrell Science Centre, Macclesfield, Cheshire SK11 9DL
Dr Jacqueline Mitton, RAS Public Relations Officer