Geminids

Geminid info from Terry. From a quick look at the weather it looks as if Wexford will be under the least cloud tonight.

1. GEMINIDS: The best meteor shower of the year, and perhaps the best we'll see for a few years, is approaching! (Next year, and in 2006, they will be affected by moonlight.)

The Geminids are now by far the best of the annual showers, with peak rates of about 120 per hour in excellent conditions, much better than the Perseids or normal Leonids. This year the Moon will be out of the way, giving dark skies if you can get away from light pollution. They start about Dec 8 and activity continues to build towards maximum, then fall off until about about Dec 15/16, but the peak of activity should be on the night of Dec 13/14. Different authorities give different times for the actual peak: Neil Bone (BAA) says about 16.00 UT, others say about 24.00.

But in the case of the Geminids it's not that critical, as the peak is fairly 'broad', not sharp like the Quadrantids or some of the extra 'Leonid bursts'. In other words, levels can be quite high for 8-10 hours before, and 4-6 hours after, maximum. And the radiant is above our horizon for all of the hours of darkness in Ireland, although it's rather low in the NE just as twilight ends in the evenings: it lies just above Castor.

So it should be possible to see some activity from about 18.00 onwards, increasing steadily towards midnight and the wee small hours. Then, depending on just when the peak occurs, it could continue at quite a high level almost to dawn, or gradually decrease again as the radiant gets lower in the West.

But if it's clear on Monday/Tuesday evening, head for a dark sky site and treat yourself to a real display of celestial fireworks - for free! Bring a lounger, or a waterproof rug or groundsheet + a foam mat & a sleeping bag; plus about twice as many layers of clothes etc as you think you'll need, especially for head, hands and feet; plus a hot flask of tea, coffee or soup (NOT alcohol), some choc bars or other sugar boosters; red & white torches, plus your mobile for security, and tell someone where you are going.

Ideally you want to be in a REALLY dark site, where the Milky Way is blazing down at you, and you can hardly identify the constellations because you can see so many stars! That means going at least 50 miles from Belfast & Dublin, 30 miles from Cork, 20 miles from Bangor, Derry, Galway & Limerick, and so on pro rata for smaller towns.... Such sites are increasingly hard to find, and if you can't manage that, just go for a reasonable compromise, but you certainly should aim for somewhere that the Milky Way is easily vsible. If it's not visible, you'll see less than half, and maybe only a third, of the real number of meteors!

Your eyes won't fully dark adapt for about 20 mts, but you should start to see some meteors after at least 5 minutes or so, if the radiant is more than about 15 degrees up. Later in the night if it's totally clear & dark you could be seeing several meteors per minute, sometimes in bursts of 3, 4 or 5 in close succession, maybe followed by a short gap.

Best place to look is at an altitude of about 45-50 degrees above the horizon, and about 40 degrees away from the radiant (no room to explain why!) in whatever direction the sky is darkest & clearest. The same applies to photography (use a standard 35mm camera, normal 50mm lens wide open (or closed down 1/2 or 1 stop for better quality images), a fast colour film (ISO 400 - 800), and simply keep the shutter open for exposures of 6-10 minutes in a really dark site, or 3-5 minutes in a brighter one. You'll also need a tripod & a locking cable release (+ a spare just in case), and a red torch for checking the camera. DO make sure that the lens is set to your chosen aperture (NOT set at F/11 or F/16!), and make sure it's focussed on infinity! You should also bring some clean tissues for wiping dew from the lens (check it every other exposure)

The Geminids are a very interesting shower, as the 'parent body' seems to be an asteroid (Phaethon) rather than a comet; maybe this is why the Geminid particles seem to be denser than average shower meteors, and therefore often penetrate deeper into our atmosphere before buring up.

If you want to do some useful serious observing, record the sky limiting magnitude in the zenith, the times of each observing period to the nearest minute (e.g. 22.15 - 22.50; 23.00 - 23.28; 23.33 - 00.12), and the general sky conditions - any cloudy patches, or obscuration by buildings etc. Record the number of Geminids (+ any sporadics if you like, separately) seen in each observing period. Other useful information is the estimated magnitude of each meteor, the colour if any, speed (fast, medium or slow - most Geminids are slow), and any persistant trails (called 'trains') lasting more than a second or so after the meteor itself has disappeared. If you are observing with someone else, or in a group ONLY COUNT THE NUMBER OF METEORS YOU SEE YOURSELF! Anything else seriously distorts the calculated true (ZHR) rates!
(I can give more detailed advice on meteor observing if anyone wants.)

Otherwise, just stay warm & safe, and enjoy the show!

A sky chart shoeing the approximate Geminid radiant is available from the EAAS website along with some detail to the source of the Geminids.

www.eaas.co.uk/news/geminids.html

Clear Skies



MarkDJ

Another cloudy or overcast day on Monday, with outbreaks of rain and drizzle developing in the northwest and west during the morning. The rain and drizzle will spread eastwards in the afternoon but amounts will be small in most places. During the evening, clearer and mainly dry conditions will extend from the west. Moderate, south to southwest winds will freshen for a time before veering westerly with the clearance. Highest temperatures 8 to 11 degrees Celsius.

3 Day Outlook:
The weather will be very unsettled next week with wet and windy conditions at times coming in from the Atlantic. There will certainly be some sunny interludes but spells of heavy rain will occur also giving between 25 and 50 mm of rain in places. The winds will be strong to gale force at times; initially from a south to southwest direction later predominantly west to northwest. The week will start mild but will gradually turn colder.

Clouded out again...

Can anyone tell me how I can listen to the Geminids on the radio? I have heard that you can tune to a distant FM station and then listen for it's reflection off a meteor but I tried it and heard nothing. I tuned to 88.5FM which is a BBC station in England but maybe I need an external aerial? Is there any special technique?


Mark

Mark,
it is not as easy as you think. You may be able to pick up a sporadic broadcast on FM with your regular, high quality radio/tuner, but only the bigger of the big meteors will do this for you. You would have to have an FM aerial set up akin to looking like a TV aerial to pick up many more sporadic broadcasts.

Charles here (ei5fk) is into atmospheric radio as a hobby, so he might be the better person to give you exactly what you can and can't do with what you would have at home.

One suggestion I would make is to pick a frequency a little higher, say around between 96MHz and 103 MHz - these are the greater concentrations of radio stations in almost any country. If you simply choose an 'empty' frequency on this band, and on a good night like tonight, you should pick up a few bursts at least.

Seanie.

Hello Mark and Seanie, in my opinion at between 88 and 108mhz if you are interested in meteor reflections the UK is too close, meteors work best over 800km and up to lets say 1500km, with a standard fm radio and no outside aerial attached place the radio in the clear on a south or east facing findow cill upstairs and tune around, better if you know the frequency of a high power transmitter and I cant help you there, the Geminids work when the radiant is over the horizon.
www.qsl.net/ei5fk/per2004.htm
This page shows screenshots of meteor reflections from radio hams on 144.370 using a program called fsk441 and a high gain aerial, each window is a 30 second period, at 90mhz reflections will be much better, image 1 is a German, 2 an Estonian, 3 Switzerland, 4+5 Italian, 6 Austrian, 7-13 Finland, 14-15 Denmark, 16 Holland, 17 Slovenia, 18 Iceland, 19-20 Germany and finally 21 Denmark
Wish I had a clear night to take my ETX-70 out
Have fun
Charles