The most partial of eclipses

There’s a partial eclipse of the Sun on 11 August. Hooray! But it’s only visible from the far north of the British Isles. Boo! (Unless you live there, of course.) And to make matters worse, it’s about the smallest partial eclipse that you could ever see. Double boo! Forget that sky-turning-dark business. Most people would never notice it taking place. Even from John O’Groats you’ll need a reasonably good setup to observe it, and from Orkney or Shetland the situation is not much better, because only a tiny bit of the Sun is covered by the Moon.

The eclipse is visible only well north of a line from Uig on Skye to Dornoch in Sutherland. If you’re in the area then you need to be as far north as you can get. From John O’Groats the eclipse begins at 9.33 BST and mid-eclipse is at 9.46. By 10 am the Moon has left the Sun’s disc completely. From Lerwick in Shetland it lasts less than 45 minutes and maximum eclipse is at 9.50.

Partial eclipse diagram
The greatest partial eclipse visible on 11 August 2018 as seen from Lerwick in the Shetland Isles at 9.50 am

For such a small eclipse, there’s a big danger that people will take a chance on viewing it using some unsuitable method rather than getting the proper apparatus. But the Sun really is bright enough to blind you, so don’t take any chances. If you haven’t got a safe viewer, give it a miss. Some safe methods, such as pinhole projection methods as suggested for larger partial eclipses, won’t work, as the area covered by the Moon is so small. You’ll need to view it through either an approved solar viewer, a telescope or binoculars with a proper filter over the front, or by projecting the Sun’s image. For information on the first two methods, look at Lucie Green’s video made for the much larger eclipse of March 2015. The mirror method suggested there will just work, if you are far enough north. For some tips on projecting the Sun’s image, we have a help page.

You might wonder where you’d have to go to see the Moon cross right in front of the Sun. The answer is several hundred miles above the north pole! This is a case when the central part of the Moon’s shadow misses Earth altogether, so no-one on Earth gets to see a total eclipse.