Originally based on Dark Sky Diary by Steve Owens www.twitter.com/darkskyman
The first meteor shower of 2012 is the Quadrantids, the peak of which falls on the night of the 03/04 January 2012. The Quadrantids shower has one of the highest predicted hourly rates of all meteor showers, comparable to the two great annual showers, the Perseids and the Geminids, occurring in August and December respectively. However unlike the Perseids and Geminids, the Quadrantids peak is very narrow, occurring over just a few short hours.
The predicted Zenith Hourly Rate (see my previous post about ZHR and what it actually means here) for the Quadrantids is around 120. The narrow peak is predicted to occur some time between 2100 UT on 3 January and 0700 UT on 4 January 2011, however the radiant of the shower – the now-defunct constellation Quadrans Muralis – is very low in the evening hours, rising higher towards dawn, and so the best viewing times are later in this run, just before dawn.
The radiant will rise due N and get to its highest before dawn due E, so look roughly in a NE direction to maximise your chance of seeing some Quadrantids. As always with meteor showers, don’t use binoculars or a telescope – your naked eyes are best. One very useful bit of equipment is a reclining deck chair, which makes observing so much more comfortable!
Let’s use the equation relating ZHR to actual observations of meteors to work out how many Quadrantids you might see:
Actual Hourly Rate = (ZHR x sin(h))/((1/(1-k)) x 2^(6.5-m)) where
h = the height of the radiant above the horizon
k = fraction of the sky covered in cloud
m = limiting magnitude
In the case of the 2011 Quadrantids, if observed from the UK, h = 15 degrees at 2100, rising to 25 degrees at midnight, 40 degrees at 0300, and 65 degrees at 0600. Let’s assume you have clear skies (haha) with k = 0.
The number of Quadrantids you can expect to see from a variety of observing sites, at various times throughout the night, is as follows:
For very light polluted sites, such as city centres, m = 3, and therefore you can expect to see between 3 and 10 meteors per hour at the peak, depending on when it occurs.
In suburban skies near a city or town centre m = 4, and you’ll see between 5 and 20 meteors per hour at the peak, depending on when it occurs.
In rural skies where m = 5, you’ll see between 11 and 38 meteors per hour at the peak, depending on when it occurs.
Under very dark skies, where m = 6.5 (i.e. where there is no or negligible effect of light pollution, like in Galloway Forest Dark Sky Park) you’ll see anywhere between 31 and 109 meteors per hour at the peak, depending on when it occurs.
Remember, all of these numbers assume perfectly clear skies. If half your sky is cloudy, cut these numbers in half!
Also remember that it depends when the peak occurs. Due to the rather narrow peak, if you observe at 2100 on 3 January you may see very few if the peak doesn’t occur until 06700. Still, it’s very much worth a look, just in case!
How many Quadrantid meteors will I see?
|Where are you observing from?||Limiting magnitude||Number of Quadrantids per hour if peak occurs at 2100
||Number of Quadrantids per hour if peak occurs at 0000||Number of Quadrantids per hour if peak occurs at 0300||Number of Quadrantids per hour if peak occurs at 0600|
|Very light polluted city centre||3||3||5||7||10|
|Dark Sky Site||6.5||31||50||77||109|