Make your own free website on Tripod.com

 

Amateur Astronomy on the Web
Back to Home Page

(Back To Homepage)

                THE LEONID METEOR STORM - Some really great observing advice

(FROM AN ARTICLE POSTED ON A LIST SERVER BY PIERRE MARTIN)
 BAD METEOR ASTRONOMY GOOD ADVICE
One should start looking for Leonids as soon as the Sun goes down.  By staying up all night, this will ensure that nothing is missed. Like many other first-time meteor watchers, if you start watching too early with high expectations you will be very disappointed.  Why? It's simple.  On November 17, the radiant (located in the constellation Leo) will not rise until near 11pm.  This means that due to geometry, it is impossible to see a Leonid meteor anytime before 11pm.  If you saw a meteor at 9pm, it was either a member of another minor shower or a sporadic, but *not* a Leonid.  Sporadics (random meteors) can be seen at any anytime of the night and they typically produce rates of about 5 per hour in the evening.
Meteor observations should be carried as a group activity at a single dark sky observing site. It's a good idea not to observe alone for security reasons and peace of mind.  If you are observing solo at a remote site, bring a cell phone for emergency use, and tell friends and family where you intend to be.  It's also a wise idea to have a emergency winter car kit with basic survival tools.
Why do all these crazy astronomers bother to drive long distances away from the city just to be out in the middle of nowhere?  It's too dark and cold.  Why not just step outside in my city/suburban backyard to see if there's anything interesting happening up there.  If not, I can just crawl back in my warm bed. We may seem nuts to go through all this trouble, but remember that there's a very good chance that the morning of November 18 will produce more meteors than most of us has seen in our entire lifetime. This kind of event is one of nature's rarest AND most spectacular! Many observers, both amateurs and professionals from all over the world are serious about seeing this year's Leonids and have been preparing for this since a long time.  Many will try and view them from dark skies as far away from city lights as possible to get a better view.
Since the peak is predicted to be a sharp one on the morning of November 18, observations the night before and after are much less meaningful.  I just wouldn't see much on these nights, right? Actually, don't rely only on the predictions for the peak night.  We can still get unexpected surprises too, even on nights away from the maximum!  During the 1998 Leonids, an unexpected bombardment of fireballs arrived 16 HOURS before the predicted peak.  Many of these fireballs exceeded the brightness of the Full Moon.  Although such incredibly bright meteors are not expected to return this year, it's still important to try and cover as many nights as possible around the peak to help us have a better understanding of the stream.
The radiant is in the constellation Leo, therefore most meteors will be seen very close to Leo. Nope, you'll see them going everywhere in the sky.  Think of the radiant as standing on railroad tracks and seeing the rails converge into one single point at the horizon.  It's simply perspective.  It's the same thing with a meteor shower.  All the meteoroids from the Leonids stream hit our atmosphere in parallel paths.  An observer on the ground will see that meteors radiate from a single point in the sky called the radiant.  We call them Leonids because their radiant is located in the constellation Leo.  Does this mean that the Leonids will be concentrated only around Leo?  No.  You'll soon notice that many of them can appear no matter where you look in the sky.  You can tell they are Leonids because if you trace an imaginary line behind the path of the meteor, it will lead all the way back into a point located within the sickle pattern of Leo.  The sickle, representing the Lion's head is an asterism of stars with the shape of a backwards question mark.
Since the Leonids have the fastest entry velocity of any other meteor showers (71 km/sec), they will all appear extremely swift visually. Although all Leonids slam into our atmosphere at the same entry velocity, perspective will make the short ones you see near the radiant appear to move more slowly.  It's an effect called foreshortening.  If you happen to see one directly on the radiant, it will look like a brief star-like flash without any motion at all because it's seen coming directly *toward* you (don't worry, all Leonids burn up in the upper atmosphere and won't hit you).  On the other hand, Leonids seen further away from the radiant will appear to move swiftly against the starry background.
Leonid meteors are too fast and brief to photograph.

Leonids usually last only a fraction of a second, and they are indeed fast smashing into our atmosphere at 71km per sec!  The easiest way to photograph meteors is to mount a 35mm SLR camera (capable of doing time exposures with cable release) on a tripod.  Use a 35mm or 50mm lens, ensure it is wide open (f/1.4 or f/2) and be sure to set the focus to infinity.  Use a fast film (ISO 400 to 1600).  Whether you use black and white, colour film or slides is more a matter of personal choice.  Black and white is often useful for analysis, but colour is more esthetic.  The camera should be aimed about halfway up, and roughly 40 degrees from the radiant.  This area in the sky will produce meteors with longer paths.  If you have a dark sky, try exposures ranging from 10 to 25 minutes depending on the shower's strength.  If you're located at a suburban sky with some light pollution, expose your camera for no more than 5 minutes.  Do you have an extra camera body lying around in the closet?  If so, why not use it as well?  More cameras aimed at the sky will improve your odds of catching a streaker on film!

The best way to see meteors is to "look straight up". Actually, that's not quite true.  If you look straight up, that means looking near the zenith.  That area in the sky has the least thickness of atmosphere.  Looking lower in the sky will make you stare into a larger chunk of the atmosphere which improves your chances of seeing more meteors.  Don't look too low or else haze or sky glow will become a problem.  A good compromise is to center your field of view about 50 to 70 degrees high (a little more than halfway up) in the sky.  It's also crucial to face in a direction of the sky that is away from the glow of a major city.
If observers are keeping track of the numbers of meteors they are seeing, they should combine the data together with other individuals beside them as a way to increase the final totals.  Ideally, observations are more meaningful if the entire sky is covered. Meteor counts should not be combined.  Record only your own observations.  Decades ago, meteor observers would often pool observations together for all-sky coverage.  However these days, meteor observing is a solo activity. The International Meteor Organization (the clearing house for meteor observations worldwide) says that an observer's report should normally be done individually. Today's standard ZHR (zenithal hourly rates) for meteor showers is calculated for a single observer's field of view if the shower's radiant was located at the zenith, and assuming LM=6.5 skies.
The best way to keep warm during a cold night is to have the car running with the heater set at maximum. Don't do that! On the short term, a hot car will warm you and feel nice. Do that repeatedly and that sucks the energy out of your body. You will "feel" colder much faster every time.  Soon enough, the fatigue will also creep up as your body is stressed due to the rapid changes from cold to very warm air.  You'd be much better off to bring exaggerated amounts of winter clothing.  If you feel cool, you can always add more layers.  If you plan to stay out for a few hours, get yourself a supply of disposable chemical heater pads.  Sports and camping stores (such as Canadian Tire or Sports Chek) often sell them for only a few bucks.  They work extremely well in keeping your fingers and toes warm for up to 12 hours!  Don't forget a warm sleeping bag and tons of blankets to wrap yourself up.  Bring a lawn chair to avoid lying directly on the ground.  A general rule of thumb is to dress as if it was three times colder.  November nights can be really nippy.  Meteor observing was once referred to as the "coldest hobby known to mankind", so be prepared!!
Eating chocolate bars and drinking lots of Jolt Cola all night-long will keep me going with enough energy. Lets just say that this is very good if you need a quick dose of instant high energy.  It'll work for some time.  After a few hours, you might lose all that energy quickly?  Try a good healthy supper before your observing night and avoid junk food.  As for midnight observing snacks, try a warm drink (not alcohol), fruits and cookies. Hmm... oh what the heck... donuts would probably still be good :)
A great Leonid storm would be a threat to Earth orbiting satellites.  By the way, do any of these things ever hit the ground? We may see quick bursts of Leonids leading us to believe that they are very close together.  In reality, there is *lots* of empty space between all these tiny dust particles.  Even a great meteor like the one from 1966 (with rates of 40 meteors per second) would be only a minor threat to the Space Station and other satellites.  Space Agencies around the world are still going to take some precautions with their billions of dollars worth of orbiting instruments and observatories, ...just to be on the safe side.
The year 2001 is really our last chance to see a great Leonid storm.

Only a few years ago, we all thought that 1999 was our last chance of seeing a meteor storm.  However, meteor experts now have a much different way of predicting the Leonids.  By carefully looking at the individual dust trails caused by previous passages from comet Temple-Tuttle, astronomers were able to predict the last few years' Leonid displays with very good accuracy.  The success of recent past predictions is the reason why so many observers are excited by the upcoming Leonid displays...

The the best is yet to come!  Some astronomers predict that 2002 will actually be a Leonids Grand Finale.  That year, a display of epic proportions (10,000 to perhaps 30,000 meteors per hour) could storm over the west coast of North America.  Unfortunately, the one major problem for 2002 will be a Full Moon during the peak washing all but the brightest meteors.

 

Be sure to consult the Montreal Centre Events page to learn of any Leonid Observing sessions

If you'd like to read more about the 2001 Leonid meteor shower, check out this fine article from the North American Meteor Network which was posted a few days ago...

  Clear (and dark) skies to all for the morning of November 18,

 Pierre Martin

(Back To Homepage)

  MMV, Montreal Centre
The Royal Astronomical Society of Canada
P.O. Box 1752, Stn. B
Montreal, QC, H3B 3L3 Canada
Contact us by e-mail