Get ready for the eclipse of the year

A partial eclipse of the Sun takes place on the mid-morning of Thursday, 10 June as seen from the UK. Although this won’t be anything like as spectacular as a total solar eclipse, it will be interesting to watch – but you need to take precautions to observe it safely.

During a partial solar eclipse, the Moon moves slowly in front of the Sun, appearing in silhouette against the bright solar disc. The Sun looks as if it has a bite taken out of it. But because the Sun is so blindingly bright, the small obscuration caused by the Moon won’t make it any safer to look at directly, so you need to use a suitable observing technique.

Alternatively, we will be live streaming the event on our Facebook and YouTube channels, weather permitting. The live stream will start at 10 am with views of the Sun only, then from 10:45 am to 11:45 am we’ll have a live chat show with guests talking about eclipses past and present. You can watch the show by going to facebook.com/popastro or youtube.com/popastro or twitter.com/popastro You can also view on a smart TV by going to the YouTube option and searching on popastro.

The Sun as it will appear from the UK during the partial eclipse. Photo: Robin Scagell

How to view it safely

Because the Sun is so bright, sunglasses are completely useless. If you have proper eclipse glasses from a previous event you can use those, provided they are still in good condition and haven’t suffered scratches or other damage. Never use improvised filters such as bin liners. Although they may appear to cut down the Sun’s brightness, giving you a false sense of security, they usually transmit infrared light, which conveys heat into your eye. Because it looks dim, the reflex action that normally protects your eye doesn’t prevent you from staring at it and you feel nothing until you scorch your eyeball.

Fortunately, if you don’t have safe filters, there is a neat method of viewing the eclipse using nothing more than a small mirror. It needs to be a flat mirror, not a concave or magnifying mirror. All you need to do it to completely cover it with paper apart from a hole just a few millimetres across. Reflect the Sun’s light onto a white surface a metre or more away, and you’ll see an image of the Sun. The hole doesn’t even need to be circular or evenly cut.

A hole 5 mm across will give a nice image of the Sun about 50 mm across, five metres away, but if you have less room use a smaller hole and a shorter projection distance. If you can project the image into a room, it will be easier to view against the background. The image will move slowly as the Sun moves through the Sky, so you’ll need to reposition the mirror from time to time. You can practice the method in advance so you are ready for action on the day itself.

mirror
Cover a mirror with paper with a small hole cut in it. It doesn’t need to be circular!
How to set up your projection. The mirror should be at a right angle to the wall. The image is upside down compared with the direct view.

What you’ll see

At the start of the eclipse, some time after 10 am BST, a small bite will appear at the upper right corner of the Sun. This will progressively get larger. moving from right to left, until by mid eclipse, about 11:15, around a fifth to a quarter of the Sun will be covered by the Moon. Then the bite starts to get smaller, and it’s all over by about 12:30.

The exact timings and the amount of the Sun covered vary with where you are in the UK. The farther north and west, the more of the Sun will be obscured. The diagram below shows the timings and amount covered as seen from various cities.

About the eclipse

In this case, no total eclipse will be seen from anywhere on Earth. The Moon passes directly in front of the Sun as seen from a line from Canada to Siberia, crossing the North Pole. On this occasion it happens to be at a greater than average distance, so it will appear slightly smaller than the Sun’s disc and a ring of bright light will remain around the Moon. This is known as an annular eclipse.

The track of the annular eclipse is shown in grey. The Moon’s shadow moves from left to right.