Object
Phases, rise and set times, earthshine, supermoons and eclipses: everything the Moon does to your night, with the exact figures for where you stand.
On Monday 14 September around midday, a 12 % crescent Moon will pass in front of Venus, magnitude -4.75, under a Sun standing 40 degrees high. From Paris the planet vanishes at 11:26 and re-emerges at 12:34; from London the Moon rises with Venus already hidden. The disappearance itself takes a minute and a half: Venus is a disc, not a point. City-by-city times, and the method for seeing a planet in daylight.
Venus peaks at magnitude -4.8, yet its lead over the Sun melts from 61 minutes to 15 in a single month. In between, the Moon will hide it in broad daylight on the 14th, the equinox falls on the 23rd, and the full Moon of the 26th will rise barely later each evening. The month's programme, computed for Western Europe.
Tonight, shadows on the Moon are seven times as long as the relief that casts them. On 27 August they will be a tenth of it. A factor of seventy in seven nights, and it comes down to a single angle: the Sun's height above the lunar ground. Here is the arithmetic, evening by evening.
The Earth's shadow will cover 96.6 % of the disc. But from Western Europe the Moon sets before the eclipse ends, seven degrees above the horizon, in a sky already turning grey. From the Caribbean and North America the whole thing happens high overhead in full darkness. Here are the times, the altitudes, and where you actually want to be.
Between 21:10 and 21:55, low in the west-south-west, a crescent lit to 11.9 % passes within seven degrees of Venus. It is also the best evening this month to see the dark limb of the Moon lit by the Earth. Here are the two quarter-hours that matter, and the arithmetic of what is doing the lighting.
On the same evening, western Europe will watch the Sun set as a crescent, then the best meteor shower of the year fall through a moonless sky. That is no coincidence: it is the same Moon doing both.