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Astronomy Know How
Helping you See the Night Sky - Newsletter No. 14 December 2007 |
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In this issue: |
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December's Highlights
December promises to be an exciting month for astronomers everywhere. We have the Geminid Meteor shower, a superb chance to see Mars at its best and the Moon muscling in on the action with a lunar occultation of the planet visible from the further reaches of northern Europe on Christmas Eve. So if you live in north east Scotland or Scandinavia you should see Mars disappear behind the Moon in the early hours of the 24th. We also have the Geminid meteors to give us some celestial fireworks on the night of the 13/14th of the month and of course December hosts the winter solstice - the shortest day and longest hours of darkness for those of us in the northern hemisphere on the 22nd at 06h 08m UT (Universal Time; the equivalent to GMT or Greenwich Mean Time). After this the sun will 'change direction' and start to appear to move northwards again. Saturn is now starting to show itself again quite well in the morning hours. It will have a slightly odd appearance as the tilt of the planet from our point of view means that the beautiful ring system will seem quite thin. You can find the planet near to one of the rear legs of Leo the Lion and not far from the galaxies M105, M95 and M96. Venus is an easy object to find in the early morning skies rising about 4 hours before the Sun in the east. On the 5th of the month it is joined by a waning crescent Moon and with the bright star Spica in Virgo the Virgin nearby, would make a lovely target for a budding astro-photographer. For comet enthusiasts, Comet8P/Tuttle is now back in our skies. It is travelling southward from its position near Polaris the Pole Star and brightening as it goes. By December 21st it can be found just north of the central star in the 'W' of Cassiopeia and by the end of the month it will be in the vicinity of the faint galaxy M33 in Triangulum, where it should be about magnitude 5.7 or just within naked eye visibility. A pair of 7x or 10x50 binoculars should show it easily. |
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Mars at opposition
Mars reach opposition (exactly opposite the Sun in our sky) on December 24th. This means that it is visible all night and will be due south at midnight UT. It will also appear a a full disc rather than a gibbous phase that has been seen up till now. From mid-northern latitudes it will also be respectably high in the night sky and will appear at its largest (16 arc minutes across) on the 18th. If you have a telescope it will need a fairly high power to show any features, but be careful here, as high magnification can make the planet appear a fuzzy pink blob if you go too far. So be prepared to experiment with different powers to see how much the atmosphere and your telescope can stand. The features on Mars (if they are not blotted out by a dust storm) can be quite subtle and can take some practice to see them. Let you eye relax and take a few deep breaths to charge your brain with oxygen as this can help you to see the detail. A Wratten #21 orange filter can also help the contrast of these features as can some more specialised 'Mars' Filters. An interesting view seen with the naked eye occurs also on the 24th when the Moon will appear in conjunction with the planet and will seem to scrape past or even occult it depending on where you are observing from on planet Earth. If you live in the north east of Scotland or Scandinavia the Moon will seem to pass in front of Mars in the early hours (around 3:00am). This could be another photo opportunity? |
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December's Geminid Meteor Shower
The Geminid Meteors should put on a good show this month with up to 100 meteors an hour being predicted. Maximum activity will occur around 11:00UT on the 14th of the month. This is obviously daylight for European observers, but keeping watch through the nights of the 13/14th and the 14/15th should be rewarding. If you are really keen on observing meteors, activity in fact starts on the 7th and continues through to the 16th. The Geminids tend to produce slow meteors, so can be good targets for astro-photographers as they will be easier to capture than the fast moving Perseids that we had back in the summer. If you plan to do this, then it is best to use a digital SLR camera with a normal or wide field lens set to its highest usable ISO setting and the widest aperture. USe short exposures of 30 to 60seconds each and aim the camera 30 to 60 degrees away from the radiant point of the meteor shower. Good luck. |
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Orion
This month I've chosen to concentrate on one constellation rather than mention a few good deep-sky objects, as Orion the Hunter holds a wealth of fascinating objects to study in itself... It is now riding high in the south by midnight in mid December. Anyone who has the slightest interest in astronomy must surely know the constellation of Orion and has probably heard of the Great Orion Nebula. This is one of the few regions of gas and dust in deep space that can be seen with the naked eye and is discernable as a misty patch of light hanging from the well know sword belt of Orion. If you turn a pair of binoculars on to this, you will be rewarded with a glorious sight of swirling gas that is light by the absorption of radiation from the stars embedded within it. This nebula is also known as M42 (number 42 in Messier's famous catalogue) and if you have a telescope then even with a low power eyepiece the nebula will fill the field of view. A higher power should reveal the trapezium stars at the heart of the cloud, new born stars the ultra-violet radiation of which is the powerhouse that lights up the nebula. If you can drag your eyes away from M42 the Orion plays host to many other worthwhile sights such as the Running Man Nebula or NGC1973 which lies just to the north of M42. There are clusters galore as well, such as NGC1981 nearby and NGC1980 to the south of the Great Nebula. In fact Orion is just packed full of amazing sights to study through binoculars or a telescope. If you would like to try your hand a photographing the Nebula then a minute or two's exposure on a high ISO setting should reveal the rosy pink colour of the nebula. This colour is quite real although too faint to be detected by the human eye and is due to ionised hydrogen emitting light in the red part of the spectrum. |
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Tip of the Month
Dealing with dew... Tip: This time of year can bring cold clear nights but also moisture laden air. This water likes to settle on glass surfaces such as your telescope lens. There are several ways to tackle this problem including using a hair dryer! However a quick and easy way is to make a 'dew shield'. Some telescopes already come with such a device, but if your doesn't you can make one out of thin card rolled into a tube to fit to front end of your telescope. Ideally you should use black card to minimise internal reflections. The tube should extend 6 to 8 inches or 15cms to 20 cms in front of the objective or corrector lens of your telescope. If you already have a dew shield fitted to you telescope but are still experiencing problems you can always add more length to this using the same method. Of course the card will eventually get damp and disintegrate, but it is easy enough to make a new one! |
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Here are some links to some other recent news stories that I thought you would find interesting...
Italian Scientist Discovers a New Comet Andrea Boattini, Italian astronomer who currently works in the United States at the "Mount Lemmon" Observatory, Arizona, has recently discovered a new comet, called C/2007W (Boattini). The announcement has been given on November 23rd by the International Astronomical Union. more... UK Plans Withdrawal From Telescope Teams "This decision is a serious mistake and a shock to all of us, " Michael Rowan-Robinson, society president, said in a press release more... Is The Earth Unique In The Universe? Despite what you may have heard, astronomy is probably the world's oldest profession. Which makes "Are we alone in the universe?" a good candidate for the world's oldest riddle. more... Strewth Mate, Where's The Southern Cross Gone? The night sky in Sydney is now reported to be so bright from streetlights and other light pollution that one of the five stars in the famous constellation has faded from view and another is expected to be out of sight within five years. more... |
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DO you want to learn more about the night sky and how
to use telescopes and binoculars to see it better?..
My online course gives you all the essential information to be a good astronomer, without lots of jargon or difficult maths. You'll get loads of free bonuses and it also has videos and animations to help make the explanations clear and concise. So if you want to know what Sir Patrick wished for... ...please take a look at my eCourse called 'Basic Astronomy with a Telescope'. It's what Sir Patrick wished he'd had when he started out in astronomy! |
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