What’s Up! December 2019

A monthly look at astronomical events in the sky and on Earth

One really has to wonder whether we are “poco loco” to choose astronomy as our hobby. We’ve just had the cloudiest and wettest couple of months that I can remember for some time, and although we may have a few clear nights in the first week of December, the Met Office isn’t forecasting much in the way of clear and stable conditions for the rest of the month. Still, mustn’t grumble. Let’s at least take advantage of the odd observing night that happens to come our way and be grateful for small mercies. Important thing is to make sure that telescope is in tip-top condition and ready for action if the opportunity presents itself.

The Moon

Best seen as a waxing crescent low in the SSW after sunset on the 1st, and getting higher and higher each evening through first quarter on 4th and on through its gibbous phase past the weekend of the 7th/8th. And for the early risers amongst you, the Moon is well seen at around 7 a.m. from the 17th to the 23rd. Why oh why should I observe it then, I hear you ask. Well, because the surface features are illuminated from the east (as we see the Moon) rather than from the west after full moon, and can look very different in the lunar ‘afternoon’ than in the morning.



May be glimpsed low in the SE before sunrise but probably not worth looking out for. Better to wait for  the evening apparitions in February and April next year.


Venus is just beginning to emerge from behind the sun in December, and may be spotted low in the SSW after sunset. It’s a little to the left of a 2-day old slender crescent moon on the 28th. Venus will in fact be a fine sight in the evening skies right through to the end of May.

Mars, Jupiter and Saturn

Mars is only visible in the SSE in the morning sky and it’s only 4 arc seconds in diameter. Wait until nearer its opposition in October.

Both Jupiter and Saturn are too close to the sun to be observable in December.


Uranus is conveniently placed for observation in December. Please see November’s What’s Up for more information and a finder chart.


Neptune reached opposition in September, but is still observable in the early evening this month. As for Uranus, please see November’s What’s Up for more information and a finder chart.

Geminids Meteor Shower Peaks on the 14th December

This shower – one of the most famous showers of the year – will be active from the 4th to the 17th of the month.  So, unfortunately, will be the Moon, and on the very night of peak activity, the Moon is right there, in Gemini! The radiant culminates (reaches its highest point, in the south) at about 0200, when one might expect to see about 110 meteors per hour if moonlight didn’t brighten the sky. I really hesitate to advise the best time to give it a go. It could be between the 14th and 17th and any time after 9 p.m., but don’t get too excited.

Non-Solar System Objects

Deep Sky

These are best seen when the Moon is out of the way, and that’s in the second half of the month. The sky chart below (looking southwards from the zenith) shows the position of the objects listed.

Deep sky objects visible in December
Image captured from Stellarium planetarium app

M31 – the Andromeda Galaxy

See the entry about this in November’s What’s Up


There’s a similar galaxy to M31 not far from it. It’s the M33 Triangulum galaxy. It’s the one in the highlighted square.  M33 is smaller and much fainter than M31 and we’re seeing it square on, so its surface brightness is even less than M31’s. It’s quite a challenge to detect it. Don’t attempt it under light-polluted skies or if the sky is even a little hazy.

The Double Cluster in Perseus

Lying half way between the ‘W’ of Cassiopeia and the last star in the line of stars heading that way from alpha Perseus (Mirphak) lies the beautiful and famous double cluster sometimes referred to as the ‘Sword Handle’. It can be seen with the naked eye, is very nice in binoculars and magnificent in a telescope. It’s twice the angular diameter of the moon so use a wide field low power eyepiece for the best view.

The Pleiades

The most famous and brightest star cluster in the sky, and the herald of winter. The ‘Seven Sisters’ is in fact a cluster of nearly 1000 stars, up to 14 of which can be seen with the unaided eye by people with perfect vision. Most people can see five stars at least. The cluster is nearly two degrees across so, like the Double Cluster, requires a wide field eyepiece. The Wikipedia article is well worth a read.

Passes of the International Space Station (ISS)

The ISS is visible on quite a few days in December, and notably in the first two weeks. See the Heavens-Above web site for more details. Here is a link with all fields relevant to York selected.

Space News

For up-to-date news on space missions, rocket launches etc. scroll https://www.space.com/32286-space-calendar.html

Clear skies and good viewing.

John Rowland 27 November 2019

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