|
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. |
