Observing the Leonids
November brings an increase in the meteor activity we are likely to observe from New Zealand. In the early part of the month, the 2 Taurid meteors showers are with us, although they don't usually bring about spectacular meteor displays.
The shower that has excited meteor observers over the past few years is the Leonids. Normally a reliable, yet quiet meteor shower, every 33 years or so, the orbit of the Earth in relation to the path of Comet Temple-Tuttle means the Earth passes through the denser parts of the cometary debris that follows the orbit of the comet. The years 1998-2001 were years ago identified as years when the Leonid meteor shower were likely to be spectacular. There had been some quite spectacular displays in 1933 and 1966. So we may have to wait until he early 2030s for the next spectacular display.
I observed the Leonids from Hawaii on the morning of 17 November, 1998 (Hawaiian time) from a site on the lower slopes of Mauna Kea. I could only watch around 25% of the sky at any one time, but over a three hour period, I observed around 140 Leonid meteors. If I could have observed the whole sky, and the radiant had been near the zenith, I might have seen 4 or 5 times that number.
The peak of the Leonids, in view of observations made in the last few years, appears to be very short - just a very few hours. We like to think we know where the best observing place is likely to be, but predictions have proved to be a little astray in the past.
The problem we have in New Zealand is that the radiant point, which is within the 'sickle' of Leo, rises only an hour or two before the commencement of dawn.(the further south you are, the worse it is). Thus, from New Zealand we can only observe 30% or so of the meteors that might be seen if the radiant was high in the sky.
Given that the radiant is low in the north-east, observers will need a site with a dark sky to the north and east and from there up to the zenith. Almost all the meteors will be observed some distance from the radiant point. So it is much better to look a minimum of 15-20 degrees away from that point. You will be able to identify a Leonid meteor quite easily. Note it's path in the sky, and its length. Then take the point where you first saw the meteor, and trace a path back from that point in exactly the opposite direction to which the meteor travelled, and for about the same distance as the meteor travelled. If that brings you to a point around the 'sickle' of Leo, you will have observed a Leonid.
Leonids are noted for leaving brief trains and trails, which may be visible for several seconds. One Leonid I observed left a smokey trail visible for several minutes.
So I guess all I can say is - happy meteor watching. Don't forget to wrap up warm and have a hot drink handy. If you get cold, the quality of your observing will be compromised. Meteor watching is a good group activity, so get some of your colleagues in on the exercise. If you do this, don't forget to record what part of the sky each observer was designated to look at. Very important. OK - go to it.
Next month we'll take a look at the prospects for the Geminids.
The chart shows a field of view to the north east about 1 hour before sunrise. The width of the field is about 45° and its height about 40°
The + near Regulus marks a point to the north east with an altitude of about 20° from mid South Island and about 4° higher from the central North Island. Stars to magnitude 5.5 are shown Those 3.5 or brighter are marked also have their magnitudes shown, without a decimal point.
Chart prepared with the aid of GUIDE 7.0.