December 2013

 

Moon                         

                                                    

New                                                    3rd   08:10  --  16:40              

First Quarter                                      9th   12:03  --  00:00              
Full                                                     17th 16:21  --  07:51               
Last Quarter                                      25th 00:00  --  11:33              

 

So far only the odd cold snap, but generally quite mild, with grass still growing well into the end of November. The new solar filter works well, but is restricted in use because of the trees at Austerfield, so we are unable to observe on sunny afternoons.

 

Planets

Mercury will rise in morning twilight on the 1st at 6:45am in the company of a very thin crescent moon 7° to the right, Saturn again 7° to the right and comet ISON 12° to the left, though the comet even at mag 0.9 will be difficult to see. Mercury will be up an hour and a half before the Sun so should be bright enough to see at mag -0.7. It will be making its way back towards the Sun from then, so will, by the 10^th, rise only 50 mins before the Sun. It's not safe to seek it with optical aid after the 14th.

Venus rises on the 1st at 11:45am and with care and a good goto telescope, its bright, mag -4.6/38arcsec and 38% illuminated.disc, could be found in daylight. But for the rest of us we'll have to wait for evening. It will set at 6:15pm, about 170 mins after the Sun. This situation will continue all month but with the time available after sunset diminishing till by month's end it will set an hour and a half after the Sun. It will be coming towards Earth on its orbit during the month and by the 31st it will be brighter at mag -4.4 and bigger at 59arcsec and show a phase of 4%! A very thin crescent worth a try with a camera and a long lens.

Mars will rise on the 1st at 1am, a small mag 1.2/6 arcsec disc in Virgo. It will start to fade from about 6:30am in the dawn twilight. The situation will continue with little change all month with the planet getting a little earlier each day, so that by the end of the month it will rise at 12:30am. It will however, be a bit brighter at mag 0.9 and bigger at 7 arcsec, on its way to closest approach in April 2014, when it should get to mag -1.4 ans 15 arcsec in diameter.

Jupiter will rise at 6:45pm on the 1st, a mag -2.6/45 arcsec disc, and be available till the dawn twilight starts to lighten the sky at about 6:30am. By the end of the month it will rise at 4:30pm in evening twilight so we'll have all night to study its 47 arcsec, mag -2.7 orb. A good appearance for the planet as it will rise to 59° above the southern horizon. Get your cameras and webcams out for it this winter.

Saturn rises on the 1st at 6am in the company of a thin crescent moon to the right, a mag 0.6/15 arcsec disc. Unfortunately dawn spoils things within an hour and a half. It sets a little before the Sun in the west so is not at its best this month. However by the 31st, it will rise at 4:15am and will be with us for about 3 hours, with little change in size or brightness.

Uranus will rise at 1:45pm on the 1st in broad daylight, so will be available from the end of evening twilight, about 5pm till it sets at 2am, a small blue disc of mag 5.8 and 4 arcsec in diameter. It rises to 38° high in the south so is well placed for study. At the end of the month it will rise in the east at 11:45am and set at midnight, giving us a long enough time to study and try to photograph its moons.

Neptune will rise on the 1st at 12:45pm in daylight setting its tiny mag 7.9/2arcsec disc at 10:30pm. It won't get more than some 25° up from the southern horizon when it souths. On the 31st it will rise at 11am and can be seen from the end of twilight at about 4:30pm till it set at 8:30pm.

 

Meteor Showers.

This is the month of the Geminids. Better than most other showers and generally more reliable too. Slow meteors and about 120 per hour at the top of the sky can be hoped for. The peak is on the 13^th. It radiates from Gemini, but can be seen all over the sky as with all other showers. Unfortunately a fat moon will be in Aries just 70° away to the right and will control observing.

Comets.

 

Comet ISON of course, will be the centre of attention. It has come round the Sun without falling in, and be with us again, from the 1st, just on the horizon at 7am in brightening dawn twilight, so will be difficult though forecast to be mag 3.5. Things will be easier daily as it pulls away from the Sun. On the 4th it should be mag 2.6 as it rises at 6:15am, and on the 6th it should be mag 3.1 at 5:45am, just above the horizon. A week later on the 13th it should rise at 4am at mag 4.2 and be visible for nearly 2 hours. On the 18th is should rise at 2:15am at mag 4.6 and be available till about 6:30am. By the 23rd it will be circumpolar so available all night at mag 5.

I've concentrated on the possibility of seeing it in the mornings as that's when we have the longer time to observe. But it is also visible in the evenings of December. On the 11th, at 5:15pm, it should be mag 4.0, right on the horizon about 10° north of due west, and be gone by 5:30pm. The Sun will have dropped below the horizon, due south-west at 3:45pm, so have binoculars ready due west, on a flat horizon. On the 18th, the Sun will set at the same time 3:45pm, again due south-west, followed by Venus at 6pm, due SW, then by ISON at 7pm, due north-west. By the 21st, it will set at 8:45pm due nor-nor-west, at mag 4.8. During these last few days of December it will be setting in darker skies so should be easier, though fainter, cameras should find it more easily than your eyes.