Everything you need to know about the rare lunar eclipse visible over Glasgow

·4-min read
Everything you need to know about the rare lunar eclipse visible over Glasgow
Everything you need to know about the rare lunar eclipse visible over Glasgow

This coming Monday you have the chance to see a total lunar eclipse, a rare astronomical phenomenon which will be visible to those of us lucky enough to have clear skies, and hardy enough to get out of bed in the wee small hours.

Total lunar eclipses happen almost annually – approximately twice every three years – but they aren’t always visible from Scotland.

The last one that Scottish sky-watchers had the chance of seeing happened back in January 2019.

So set your alarms when you go to bed on Sunday night, and here’s what you might see.

The moon on Monday is a full moon, rising as the sun sets and setting as the sun rises, and for most of the night it will appear very much like any other full moon you’ve ever seen.

Under clear skies it will hang high in the south at midnight, before sinking towards the western horizon in the hours before dawn. As it does so, a total lunar eclipse will begin.

The first glimpses of anything happening will start at 0327 BST as the moon begins to enter eclipse, the left-hand side of the moon appearing to darken slightly in the brightening twilight sky.

An hour later, as the sky brightens towards the coming day, at 0429 BST the moon will be in total eclipse, and its entire disk will darken and turn red. At this point the moon will be very close to setting and will stay eclipsed until it sinks below the horizon at sunrise.

What’s actually happening during a lunar eclipse is that the Moon, as it orbits our planet, is passing into the Earth’s shadow. Some lunar eclipses at only partial, with the moon’s disk just glancing into that shadow, but more rarely we see a total lunar eclipse, when the entirety of the moon’s disk is in shade.

But if the Moon is in the Earth’s shadow, shouldn’t it vanish altogether during a total lunar eclipse? After all, the only reason we see the moon normally is because it reflects sunlight back to us. This is in fact what would happen if the Earth did not have an atmosphere. But our atmosphere acts like a lens, and bends – or refracts – the sunlight passing through it, sending it angled towards the Moon as it moves through our shadow.

This refracted light is why the moon doesn’t vanish during a total lunar eclipse. Instead it turns red. But why red? The colour comes from the fact that the sunlight that is hitting the Moon during a total lunar eclipse has passed through a lot of air in Earth’s atmosphere, and all of the blue light in the sunlight has been scattered out, leaving only the redder light. This is the same effect that causes sunsets and sunrises to turn the sky red. In fact, during a total lunar eclipse the Moon is being illuminated by the light from all the sunrises and sunsets on Earth combined, and turns red in our sky.

Glasgow Times:
Glasgow Times:

Steve Owens

The redness and brightness of total lunar eclipses varies depending on the weather in those parts of the Earth’s atmosphere through which the sunlight is being refracted at the time. And in this case, viewed from Scotland, the colour will be harder to see due to the brightness of the twilight sky. At this time of year and at this latitude, the sky brightens early. By the time the total lunar eclipse begins at 0429 BST the sky over most of Scotland will be bright enough that our streetlights will have switched off. The further north in Scotland, the brighter the spring mornings are.

And then there’s the elephant in the room – the unpredictable Scottish weather. Even if you do head out early and find somewhere with a clear western horizon, clouds and rain can still spoil your view. Checking the forecast before you head to bed can help, but eager sky-watchers become well used to ignoring overnight forecasts and setting their alarms just in case there’s a break in the forecast cloud.

This hopefully won’t put you off – the chance to see one of the sky’s rarer phenomena should hopefully entice you to set your alarm and invite your family and friends to join you outside on Monday morning before sunrise, to witness the moon turning red in a beautiful spring morning sky.

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