What’s up?
The month starts with a waning gibbous Moon that becomes new on the 13th. It is also the time that the Moon is closest to Earth, so the spring tides will be a little higher and lower than usual - fishers and bathers, be careful! Full Moon is on the 27th, when there is also an eclipse of the Moon. These eclipses, when the Moon passes into the Earth’s shadow, are safe to view and can be quite spectacular. See diagram and details below. All times are rounded off to the nearest minute.
1. Moon enters penumbra 27/07
2. Moon enters umbra 27/07
3. Moon enters totality 27/07
4. Mid eclipse 27/07 19:14 20:24 21:30 22:22
5. Totality ends 27/07 23:14
6. Moon leaves umbra 28/07 00:19
7. Moon leaves penumbra 28/07 01:29 During a lunar eclipse, or eclipse of the Moon, the Moon will first move into a part of the Earth’s shadow known as the penumbra. This is a region of partial shadow, and as the Moon moves into this, there is very little noticeable change. As the Moon moves further into the penumbra, it will appear to darken gradually. Finally, as it moves into the Earth’s total shadow, or umbra, the Moon will appear to change colour slowly and darken, and at the same time the curved part of the umbra will become visible on the Moon’s surface. Eventually the Moon enters totality. This is when the entire Moon is in the umbra and when it appears darkest and reddest.
The Moon never really goes completely dark because some light gets bent (refracted) by the Earth’s atmosphere and still reaches the Moon’s surface. The coppery reddish colour that the Moon takes on is due to the scattering of the Sun’s light as it passes through the Earth’s atmosphere. The degree of scattering that takes place depends on the amount of dust and other particles, or aerosols, in the atmosphere: the more there are, the redder the Moon will appear. At times when there has been a recent volcanic eruption, such as after Krakatoa, Mt St Helens and Mt Pinotuba, there would be a larger than normal amount of aerosols in the atmosphere and the Moon could then become a deep blood red colour - it’s understandable that ancient people saw these eclipses as portents of death or doom!
The Moon also plays a role as a planet and starfinder this month! From the 13th to the 16th, the waxing crescent will be close to Mercury, then Venus on the 14th, followed by Regulus, the brightest star in the constellation of Leo, on the 15th. On the 19th a quarter Moon will be close to the bright star Spica, and on the 20th and 21st it will be close to the giant and bright planet Jupiter. By the 24th and 25th, the now waxing gibbous Moon will be close to the ringed planet Saturn. Finally on the 27th, during the lunar eclipse, Mars will accompany the eclipsing Moon; a quite rare asterism.
It would be useful to mark these dates on a calendar and keep this page of the newspaper to follow the eclipse on the night of the 27th.