Wed, 25 Jul 2018
Total lunar eclipse sequence
ALTHOUGH we don’t usually see it, the Earth casts a long shadow out into space opposite the sun. When the moon’s orbit takes it directly behind the Earth and it enters this shadow completely, we see a total lunar eclipse.
The Earth’s shadow during a lunar eclipse is so big that the moon is immersed in it for over an hour.
From Newbury, the moon will rise just after 8.50pm, already fully in the Earth’s shadow. Maximum eclipse will happen
at 9.22pm and the moon will begin to leave the full shadow of the Earth at 10.13pm. An hour later the moon will clear the full shadow of the Earth and after a further hour and 10 minutes completely out of the partial shadow.
Even when the moon is fully in Earth’s shadow, some sunlight still gets to it because Earth’s atmosphere acts as a weak lens, bending the rays of the sun so that they can fall onto the moon. It will appear a bright coppery-red colour because as the sun’s rays travel through our atmosphere the blue light gets scattered more easily than the red light – so more of the red light gets through. That is why we often have orangey-red skies at sunset and sunrise.
If it’s clear, towards the end of the eclipse have a look for the planet Mars, which will be about six degrees (roughly the width of three fingers held at arm’s length) below the moon.
Co-incidentally, Mars also reaches the point in its orbit directly opposite the sun from us on July 27.
Mars will be at its closest and brightest around this time, so it’s a good opportunity to try and see its subtle surface markings and white polar cap with a telescope.
If you just have your eyes or a pair of binoculars, look out for a bright orangey star low down in the south east in the late evening. Mars is sometimes known as the ‘red’ planet because its soil contains iron oxide (rust) which makes its surface look ruddy.