December 2012


 




 Moon




Last Quarter                                       6th    00:00  --  12:01            
New                                                    13th  08:03  --  16:14               
First Quarter                                       20th  11:43  --  00:00               
Full                                                     28th  16:24  --  10:21
               

Getting colder with every month's passing. We had our first sub-zero night of the winter on the 29th of November, and it didn't look to be trying, so there are lower temperatures to come. Dress warmly for long observing nights. 


Planets
Mercury will be a morning planet. It will rise on the 1st at 6am, under 2 hours before the Sun, so can be sought safely with care. This will remain so for the first week, but then it starts to move behind the Sun and by the 20th it will be within an hour of sunrise and by the 22nd it will be too close to be observed with safety with optical instruments.
Venus will be visible in the mornings this month rising on the 1st at 5:30am, a large 12 arcsec disc of –4.0 mag. Unmistakably bright at that time in the morning with dimmer Saturn a couple of degrees above. By the end of the month it will have moved rapidly towards a position behind the Sun so that it will be more difficult to see in the much brighter dawn. It will also be a little fainter at mag –3.9 and smaller at 11 arcsec.
Mars will be an evening object, setting about 2 hours after the Sun, but at 4 arcsec and mag 1.2 will take some effort to see and show little detail on the disc. By the end of the month it will be in very much the same position, setting 2 hours after the sun and still too small to show detail so close to the horizon.
Jupiter will rise on the 1st at 4pm, at 48 arcsec and mag –2.8, and set at 8am, with us all night. On the 31st it will rise at 1:45pm and set at 5:45am. So will be with us all night all month, only reducing in size to 47 arcsec. Another very good month for Jupiter.
Saturn will rise on the 1st at 4:45am, at mag 0.6 and 16 arcsec so will be available for an hour and a half before the Sun interrupts things. By the end of the month it will have moved into Libra from Virgo, and will rise at 3am giving us a couple of hours to observe.
Uranus will rise due east on the 1st, at 1:30pm and set at 1:30am and on the 31st, it will rise at 11:30am, again due east, and will set at 11:45pm, due west.
Neptune will rise on the 1st at 12:45pm, a small 2 arcsec disc at mag 7.9. It will set at 10:45pm. At month’s end it will rise at 11am and will 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 13th and wonder of wonders, it’s a new Moon, so it won’t be in the way. It radiates from Gemini, but can be seen all over the sky as with all other showers. Perhaps worth a meteor watch, after the Annual Dinner?

 

Comets
 None to speak of. But you can look for yourselves on the Minor Planets site. http://minorplanetcenter.org/iau/Ephemerides/Comets/index.html
The latest from a few years ago, are listed there. Click on one for the ephemeris. If you like it, download it as a KML file by clicking on the KML file link. Then click on it on your desktop, which is where it’ll land when it gets to your machine. Click on it there and it will ask you to run google earth then to change it to google sky and the path of the comet will be drawn across the google sky for you. Don’t bother with any that show a mag number larger than 7 or 8. Most on the list are more than 15, which is very faint and suitable for photography only.
 

For details of satellites check http://www.heavens-above.com  and for sky charts call me at observatory@donastro.org.uk .