On 20th March, observers in a slim slice of the northern hemisphere will be treated to one of nature’s most impressive phenomena – a total eclipse of the Sun. This rare spectacle will not be visible again from Europe until 2026; even if you can’t make it to the Faroe Islands to glimpse totality, the entirety of the UK will be treated to an impressive partial event.
When to see it
Eclipse times and coverage will vary from north to south. In Edinburgh the event will begin at 08:30 UT, with greatest eclipse at 09:35 UT when the Sun will be 93 per cent covered. From Manchester, the eclipse begins at 08:26 UT with greatest eclipse at 09:35 UT when the Sun will be 93 per cent covered. From Manchester, the eclipse begins at 08:26 UT with maximum eclipse at 09:32 UT and coverage a little under 89 per cent.
In London there’ll be an 84 per cent eclipse, beginning at 08:24 UT and peaking at 09:30 UT. To see the action find a clear southeasterly horizon – at greatest eclipse the Sun will be about as high in the sky as stretching out your thumb and little finger and holding it at arm’s length, with the lower digit on the horizon.
This display of celestial mechanics is a must-see astronomical event.
How to see it
It’s important to view any eclipse safely as the Sun can cause serious damage to your vision. Never look directly at the Sun without the protection of a certified solar filter (such as the eclipse viewing glasses that come free with the current issue of BBC Sky at Night Magazine). Simply put the eclipse glasses on and you can watch directly as the Moon gracefully covers up more and more of the Sun. Just check before you put them on that there are no scratches or pinprick holes on the black lenses.
Projection through a colander
Simply hold up a kitchen colander during an eclipse and you will see that myriad small crescents – corresponding to the eclipsed phase of the Sun – are cast in the shadow. Each hole acts in the same way as a pinhole camera, projecting an inverted image of the Sun, and this works even if the holes are not round. This effect can also be seen when sunlight shines through leaves on a tree or other foliage, with the gaps between leaves acting as pinholes and creating crescents of light in the shade on the ground.
Casting the image onto a white piece of card held about 50cm away will increase the contrast, making the event easier to see, however any light-coloured surface will work. Try varying this distance to find the sharpest image, as the size of the holes in different colanders will affect the view. This method is the cheapest and easiest way for a group of people to simultaneously view the eclipse and its progress with no risk to either eyesight or equipment.
The results can be easily photographed using any conventional camera. The only downside is the size of the crescents are quite small. Increasing the distance between the colander and the projection screen will make the crescents larger, but also less defined. As such, other than the crescent itself, no details such as sunspots can be seen.
Pros: Cheap and easy, great for large groups of people
Cons: Views are quite small, no detail can be seen apart from the crescents
Projection through binoculars
To get a larger, brighter image and detail on the eclipsed Sun you need optics of some sort. The easiest way is to use binoculars to project an image onto white card. To keep the image steady, mount the binoculars on a tripod. You’ll also need a ‘light shield’ to keep the projected image in the shade.
Create this shield by placing the binoculars, objective lenses down, on the centre of a sheet of thick card. Trace around the lenses and then cut out the resulting circles to create holes in the middle of the card. With the binoculars mounted on the tripod, fix the card around the objective lenses using gaffer tape (as below), sealing any holes around the card edge where light could leak through. Cover one of the objective lenses with the lens cap.
Aim the binoculars at the Sun without looking though them – this can be tricky so it is worth practising this before the eclipse.
Hold a piece of white card about 50cm behind the binoculars and focus until a sharp image is reached. Don’t put anything in the concentrated light beam coming from the eyepiece as this is hot enough to burn. With sharp focus, this method will easily show any sunspots along with their darker umbra and penumbra.
Pros: Straightforward to set up, brighter and more detailed images than the colander method
Cons: Aiming at the Sun is tricky, care must be taken with concentrated sunlight
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