There’s plenty to see this month with the dark nights, including the planets, meteor showers, features of the moon and a variety of beautiful deep sky objects.
Both the 6th and 20th December will be good nights to observe the Moon. About 7 miles wide and 79 miles long, you should see the Alpine Valley cleft towards the upper edge of the Appenine mountain chain, outlining the edge of the Mare Ibrium.
Following that for two days after the 6th, the dark craters Plato and Copernicus will come into view. Although quite challenging to observe, they make for very intriguing viewing if you can get a clear view.
Further afield, on the 3rd after sunset, you should be able to take the opportunity to see Venus below a thin crescent moon, and both Mars and Venus the following day.
During the early part of the mornings of the 14th and 15th December, if conditions allow, you can observe the peak of the Geminid meteor shower.
Unfortunately, due to the bright light of the full moon at this time, the fainter meteors will not be seen however, the Geminids often produce spectacular fireballs, so it’s well worth observing if you get a good enough observational viewpoint.
|New Moon||First Quarter||Full Moon||Last Quarter|
|December 29th||December 7th||December 13th||December 20th|
On the 10th, Mercury reaches its greatest elongation east and can be observed low in the southwest for the first couple of weeks of December. Its angular size increases at the start of December from 5.5 arc seconds to 7 arc seconds by the 10th of the month.
It will reach viewable magnitude 0.0 on the 17th but will be impossible to view by the 19th due to the Sun’s glare. It will move to inferior conjunction on the 28th so will become impossible to view from that point onwards.
After sunset, Venus becomes viewable in the southwest and sets around 3 hours after sunset during the early part of December. That increases to around 4 hours by the latter part of the month
On the 7th, Venus moves rapidly eastwards from Sagittarius into Capricornus and brightens significantly from magnitude -4.2 to -4.4, whilst its angular diameter increases from 17 to 22 arc seconds. During that time, the illuminated face of the planet falls from 68% to around 56% meaning its brightness will stay fairly constant.
After sunset, Mars can be seen low in south but this December will not the ideal month to observe the red planet.
As it moves eastwards into Aquarius from Capricornus on the 16th, it will gradually dim from magnitude +0.6 to +0.9. The planets disc will only be 6 arc seconds wide so very little, if any detail can be observed on the red planets surface.
The giant Jupiter will reward early risers this month as you should be able to observe its equatorial bands and perhaps all four of the Gallilian satellite moons of Io, Europa, Ganymede, and Callisto as they orbit the planet.
Lying in Virgo, Jupiter will rise at 02:30 UTC at the start of the month and at 01:00 UTC by the end of December.
Its magnitude will increase slightly from -1.8 to -1.9, as well as its angular size from 31 to 35 arc seconds. By the end of December, it will reach the meridian by dawn at an elevation of 35 degrees.
Unfortunately, observers of Saturn will have a short window this month as the planet passes behind the Sun on the 10th of the month. Christmas Day will bring slight reward however, as it returns briefly, rising for an hour before the Sun and may give us a slight glimpse at dawn at a magnitude of +0.5.
Saturn will be lying low in the southeast to the left of Antares in Scorpius and may be observed with a good pair of binoculars, before the sun rises ofcourse.
Meteor enthusiasts have two opportunities to observe meteor showers during the month – the first being the Geminids, and the second being the Ursids. Details as follows:
If conditions allow, the early mornings of both the 14th and 15th December give us the opportunity to observe the Geminids.
As these nights fall just after the month’s full moon, light pollution will prevent the smaller, fainter meteors from being seen. If however you’re lucky enough to spot them, the Geminids can be incredibly rewarding with their fireball resembling qualities, so they’re well worth persisting with.
They move relatively slow so a good spot away from inner cities is advised. Unlike most meteor showers that arise from the debris of comets, these meteors are formed from debris released from asteroid 3200 Phaethon. The radiant is close to the bright star Castor in the constellation Gemini.
Thankfully, the moon will not play a huge part in affecting the best time to observe the Ursid meteor shower during the late evenings of 22nd and 23rd of December. To find them, look northwards at a high elevation, close to the star Kochab in Ursa Minor where the radiant lies.
The peak rate of 10-15 meteors per hour is not considered a lot but, there can be a far higher rate from time to time so its worth sticking it out if you can.
Deep Sky Objects
Discovered on 4 January, 1827 by John Herschel, this open cluster is located in the constellation of Orion and forms the northern part of the asterism known as Orion’s Sword. It belongs to the Gould Belt and is located approx. 1.2 thousand light-years from the Sun. Its age is estimated at approx. 5 million years.
This month, it will be nicely positioned for observation on 14th December and around midnight, it will reach its highest point in the sky. From the south east, it will be visible between 20:30 UTC and 03:30 UTC.
It rises 18° above the south-eastern horizon around 20:34 and reaches its highest point of 34° at 23:59. It will become invisible around 03:27 when it sinks to 19° above the horizon.
NGC 2232 is a bright open star cluster in the constellation Monoceros centred on the star 10 Monocerotis. It consists of around 20 stars.
It will reach its highest point in the sky around midnight UTC. This cluster is visible across most of the world at latitudes between 65°N and 74°. This month, it can be seen from the south east at a declination of -04°45’ and will be visible between 20:26 and 03:36.
It will first become viewable at 20:26 UTC , when it rises 17° above the horizon, reaching its highest point at 23:59 UTC. It then sinks to 17° around 03:36 when it becomes inaccessible.
NGC2232 is tricky to make out with the naked eye but is clearly visible through a pair of binoculars or a telescope.
NGC 2244 (Caldwell 50)
NGC 2244 is a stunning open cluster in the Rosette Nebula, located in the constellation Monoceros. This cluster has several O-type stars – super hot stars that generate huge amounts of radiation and stellar winds.
It will reach its highest point in the sky at around midnight UTC, at a declination of +04°52’, and can be observed at latitudes between 74°N and 65°S.
From the south east, it will be visible between 19:40 UTC and 04:18 UTC. At around 19:40 UTC, it becomes visible rising 19º above the eastern horizon, reaching it highest point at 23:57 UTC, 43° above the southern horizon. At 04:18 when it drops to 19°, it becomes inaccessible.
NGC2244 is too faint to be seen with the naked eye, but is visible through a pair of binoculars or a telescope.