The Big Three
The top three sights for this month.
There is a total lunar eclipse this month, the first visible from the UK since September 2015. If the unthinkable happens and clouds ruin the fun, the next takes place during the early hours of 21 January 2019, so at least the wait isn’t nearly as long. And while the UK will get to see the January 2019 eclipse from start to finish, this month’s starts with the Moon well below the horizon.
The eclipse officially starts at 18:15 BST (17:15 UT) on 27 July, when the Moon enters the weak outer penumbral portion of Earth’s shadow. As the Moon moves in towards the darker umbral shadow, its western surface will begin to darken. At 19:24 BST (18:24 UT), the Moon enters the umbral shadow and the partial phase of the eclipse begins. The umbral shadow creeps across the Moon’s face until it completely covers it at 20:30 BST (19:30 UT), the start of totality. This is academic for the UK as it all happens before moonrise. To see these early phases of the eclipse you’ll need to relocate somewhere, say, within Eastern Europe.
From the centre of the UK the Moon rises at sunset, making an appearance around 21:10 BST (20:10 UT), just before maximum eclipse at 21:22 BST (20:22 UT). This is the time when the Moon is deepest within the umbral shadow.
From the UK the dark Moon may initially be hard to see against the bright evening twilight. However, if the evening is clear it should be possible to see the dark, often red-orange coloured Moon embedded in the Belt of Venus. This is the name given to the pink band that stretches across the horizon opposite to the sunset, and it extends roughly 10–20° above the horizon. It represents the projection of the red sunset into Earth’s atmosphere. Below it is a grey region which is the local version of Earth’s shadow, projected into the atmosphere. The non-local version will be covering the Moon’s face!
Totality ends at 22:13 BST (21:13 UT) with the Moon 6° above the southeast horizon from the centre of the UK. At this time the bright opposition planet Mars also makes an appearance, 5.9° below the Moon.
The second partial sequence ends at 23:19 BST (22:19 UT), almost an hour after the end of totality. The weak penumbral shadow continues to cross the Moon’s face until 00:29 BST on 28 July (23:29 UT on 27 July). This part of the eclipse is difficult to see visually except when the Moon is near to the umbra.
The full Moon which is eclipsed on 27 July will also be the smallest full Moon of 2018, being closest to apogee. This is unofficially described as a micromoon.