Adrian Dening's Stars Over Somerset

Wednesday, 29 September 2021 17:00

Monday 4th to Sunday 10th October 2021

We'll start off with a visual challenge for the early risers on Tuesday 5th - the chance to see a 1% lit waning Crescent Moon appearing above the horizon to the east about an hour and a half before the Sun. It is the optimal position to observe this if you can bear being up at 6am local time.

If an early start isn't to your liking, on the Thursday evening you could try spotting a 2% lit waxing Crescent Moon close to the south west horizon shortly after the Sun sets.

I'm often asked what the terms "waxing" and "waning" mean.

Our Moon passes through different visible phases over a period of 29 days because it travels around us while we travel around the Sun, so all the angles keep changing. The sunlight illuminating the side of the Moon facing us varies between 0% when we have a New Moon and 100% which is a Full Moon.

A waxing moon gets more sunlight on it as the days go by or in other words it's the period after a New Moon. A waning moon progressively receives less sunlight - the days after a Full Moon.

There is an easy way to work out if the Moon is waxing or waning - if the illumination is to the right hand side, it is waxing and if to the left, waning. This is only true in the Northern Hemisphere and assumes you are looking at the Moon with the naked eye or binoculars - astronomical telescopes always reverse the image!

Moon Phase diagram courtesy of NASA
Copyright Adrian Dening and Radio Ninesprings 2021