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(meteorobs) NAMN Notes: August 2001

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NAMN Notes: August 2001
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Introduction:

NAMN Notes is a monthly newsletter produced by the North American Meteor
Network, and is available both via email, and on the NAMN website at:
http://web.infoavedot net/~meteorobs


Contents:

1. Perseids - The Legendary Shower...
2. Other Showers for August...
3. Recent Observations...
4. Upcoming Meetings...
5. For more info...


1. Perseids - The Legendary Shower...

The Perseids are probably the best known meteor shower for observers and
the public alike!

This year, the Perseid (PER) maximum falls on August 12th - a
weekend! This is a real plus for getting friends and family out to see
this wonderful show. These are fast meteors, at about 59 km per second,
and often leave trains behind them. There are many bright Perseids, so
even from a less than perfect sky location, an observer will see a
respectable number of meteors. For the best effect though, try to get out
into the country, away from the light pollution of streetlights. You will
see many more meteors for every extra little bit of dark sky.

Perseid meteor rates are expected to have several peaks - at 14 hours UT
and at 17 hours UT on August 12th. UT refers to Universal Time, over in
Greenwich, England, so calculate your local time accordingly. For example,
14 hours UT on August 12th, converted to Eastern Daylight Time (EDT) for
someone on the east coast of North America, would translate to 14 minus 12
hours equals 2 p.m. at Greenwich, which would be 10 a.m. in North America,
with the 4 hour time difference.

At maximum on August 12th, the Perseid radiant will be located at 046
degrees, ie RA 3h 4.2m, Dec +58, which is about 4 degrees north of the star
gamma Perseus, the middle star of the outstretched right arm of Perseus. The
Zenithal Hourly Rate (ZHR) is about 110 meteors per hour, visible with
the unaided eye, if an observer is out under a dark country sky, and if the
radiant, the area in the sky where the meteors seem to come from, is
directly overhead.

These famous meteors radiate from the legendary constellation of Perseus. In
ancient Greek mythology, Perseus was a hero. His mother was Danae - a human.
His father was the god Zeus, the son of Saturn and Rhea of the race of
Titans, who were the children of Earth and Heaven, which sprang from Chaos.

There was a prophesy that Perseus would slay his own grandfather, so mother
and son were locked in a wooden chest and thrown into the ocean. The
chest surfaced, and floated to the island of Seriphus, where Perseus grew
up. The king of the island, Polydectes, started to fall in love with
Danae, and decided to try to get Perseus out of the way. He asked him to
go slay the famous female monster Medusa, a Gorgon whose gaze turned men to
stone.

It wasn't Medusa's fault that she was a fearsome Gorgon. She had once been
a beautiful mortal. Poseidon, Zeus' brother, had seduced her inside a
temple of Athena. Athena, the goddess of both war and wisdom, was so
enraged that she changed Medusa into a monster, with her beautiful hair
becoming a squirming mass of snakes.

Perseus took off to slay her, outfitted with winged sandals from Hermes,
the messenger god; a sword of diamond from Hephaestus, the god of fire and
the forge; and a magical helmet to make him invisible, from Hades, god of
the underworld. He accomplished the feat of slaying Medusa without
directly looking at her by using her reflection in his shield. The blood
from the unfortunate Medusa's severed head, upon hitting the earth, created
the great winged horse Pegasus, who was caught and tamed by Minerva and
presented as a gift to the Muses, the daughters of Zeus and Mnemosyne. The
Muses presided over literature, art and science.

On Perseus' way home, he came upon the princess Andromeda, daughter of King
Cepheus, chained to a rock as a sacrifice to the sea monster Cetus because
of the vainful boasting of her mother, Queen Cassiopeia. Perseus rescued
the fair maiden and married her, then turned her intended husband, her
uncle Phineus, to stone using the head of Medusa. After further exploits,
he gave the severed Gorgon head to Athena, who placed it in the center of
her shield.

At a later time, Perseus, while attending a funeral in Thessaly,
accidentally
killed his own grandfather as the prophecy had predicted. Perseus and
Andromeda had a daughter whom they named Gorgophone, and a number of sons,
including Perses, who is considered to be the father of all Persians. His
granddaughter Alcena would bear a son named Hercules. In the end, Perseus,
Andromeda, King Cepheus, Queen Cassiopeia, the great winged horse Pegasus,
and the sea monster Cetus were all given places in the stars - and you can
see these constellations in your star maps for summer! The star beta
Perseus, known as Algol, the Demon Star, is named after Medusa - it fades
and brightens every 2.87 days, and was the first eclipsing variable star
ever discovered.

The famous Perseid meteor shower has been observed for about 2000 years,
with the first known information on these meteors coming from the far east.
In early Europe, the Perseids came to be known as the "tears of St.
Lawrence." Mark Littmann has a wonderful article on the history of the
Perseids on the Sky and Telescope website at http://www.skypub.com, and
writes:

"Saint Lawrence was tortured and killed in Rome on August 10, 258 during
the reign of the anti-Christian emperor Valerian... Citing Quetelet, 'a
superstition has 'for ages' existed among the Catholics of some parts of
England and Germany that the burning tears of St. Lawrence are seen in the
sky on the night of the 10th of August; this day being the anniversary of
his martyrdom.'"

Because the orbit of the Perseid meteoroid particles is tilted so much in
relation to the plane of our own solar system, the Perseids have stayed
fairly similar in characteristics since ancient times, and have not been
changed much by the influence of our large planets such as Jupiter. It
was Schiaparelli, the astronomer most noted for observing so-called
"canali" on Mars, who discovered that the Perseid meteors were related to
Comet 1862 III, also known as 109/P Swift-Tuttle. This was the first proven
association between a comet and a meteor shower.

The parent comet itself, 109/P Swift-Tuttle, was discovered in July of 1862
by both Lewis Swift of Marathon, New York and Horace Tuttle of Harvard
Observatory, Massachusetts. It was about magnitude 7.5 at discovery and
brightened to about magnitude 2 by early September, which is about the same
brightness as the stars in the Big Dipper. It sported a tail of between 25
and 30 degrees long, and was quite impressive! By length comparison, the
pointer stars of the Big Dipper are about 5 degrees apart. The comet
comes around to our part of the solar system about every 120 years and was
seen most recently in the mid 1990's. In November of 1992, it brightened
to about magnitude 5.0.

The magnitude or brightness of the meteors themselves is interesting as
well. Studies by Hruska and Ceplecha in the 1950's indicated that the
Perseids generally seem to be brighter before the date of maximum activity
than afterwards, but that some periods of brighter or fainter meteors do
occur. This tends to indicate some filamentary structure in the Perseid
meteoroid stream. In other words, we encounter clumps of brighter or
fainter meteors as the earth passes through different layers of long-ago
debris shed by Comet Swift-Tuttle.

This is a wonderful meteor shower to observe visually and also a wonderful
shower to try taking photos of. Traditionally, it has been difficult to
photograph meteors as they can occur in any part of the sky, and being
fast, are hard to register on your film. With the Perseid shower, there
are a lot of bright meteors and there are hundreds of them over the course
of the night in a dark sky. This increases the chances of capturing some
on film. You will need a camera that you can take time exposures with,
usually about 10-20 minutes in length, a cable release to keep the shutter
open, and a tripod or something to steady your camera if you are resting it
on a solid surface. Set the camera to wide open, ie. the smallest f-stop
that you have, or close to it, and set the focus to infinity. You should
use fast film of some sort, ASA 400 or higher, regardless of whether you
wish to use black and white, or color film.

In legend or in reality, Perseids are fascinating. We study the meteoroid
stream - and we dream about the ancient myths that spawned the
constellation the meteors come from in the sky!


2. Other Showers for August...

August is prime meteor observing season for observers! It is summer, the
nights are warm, and many people are on their holidays. It is a treat to
observe the annual Perseid meteor shower - but there are many more showers
visible over the month as well.

You will need to mark the various meteor radiants on a map. Quite a number
of radiants are located in the southeast sky, and they will be very
difficult to tell apart if you don't have a star map with you. For that
matter, you may wish to face towards the southeast as well. It is a lot
easier to tell showers apart if the radiants are right in front of you!

For easy reference, print yourself off a copy of our 4 NAMN star charts,
available at http://web.infoavedot net/~meteorobs/charts.html. These show the
constellations, RA and Dec sky coordinates, and the magnitudes of stars
useful to use as standards for judging the brightness of the meteors you
see.

One point that may not be obvious to newcomers is that meteor radiants move
a bit each night across the sky! Over several days, this is not a lot, and
you don't have to worry about it. However, from one week to the next, if
the shower is visible over a number of weeks, this change in location can
be a fair amount.

For Friday August 10th, the start of the Perseid weekend, a table showing
all the shower radiants is as follows, adapted from the IMO 2001 Meteor
Shower Calendar at http://www.imodot net/calendar/cal01.html.

KCG 284 degrees, ie. RA 18h 55.8m, Dec +58
NIA 317 degrees, ie. RA 21h 7.8m, Dec -7
CAP 318 degrees, ie. RA 21h 12m, Dec -6
SDA 349 degrees, ie. RA 23h 16.2m, Dec -13
NDA 335 degrees, ie. RA 22h 19.8m Dec -5
SIA 339 degrees, ie. RA 22h 36m Dec -14
PER 043 degrees, ie. RA 2h 52.2m, Dec +58
PAU 352 degrees, ie. RA 23h 28.2m, Dec -26

The Pisces Austrinids (PAU) reached a maximum on July 28th, but can be seen
until about August 10th when the radiant will be at 352 degrees, ie. RA
23h 28.2m, Dec -26. This is about 7 degrees up to the left of the star
alpha Pisces Austrinus, the star known as Fomalhaut. Fomalhaut is the
"mouth of the fish" or to the early Arabs, "the First Frog." These
meteors are of average velocity, at about 35 km per second. ZHR rates were
about 5 meteors per hour at maximum, but will be much lower in August.

The southern delta Aquarids (SDA), believed to be debris from Comet
96P/Machholz 1, reached a maximum on July 28th also but can be seen until
about August 19th. At midmonth on August 15th, the radiant will be at 352
degrees, ie RA 23h 28.2m, Dec -12, which is about 3 degrees down to the
left of the star psi Aquarius. The ZHR rate was about 20 meteors per hour
at maximum, but again, rates will be much lower now. These are average
velocity meteors, at about 41 km per second.

The alpha Capricornids (CAP) reached a maximum on July 30th, but can be
seen until about August 15th. On August 10th, the radiant will be at 318
degrees, ie RA 21h 12m, Dec -6, which is about 5 degrees to the right of
the star beta Aquarius, the star known as Sadalsuud, "luckiest of the
lucky." ZHR rates at maximum were about 4 meteors per hour, but rates in
August will be very low. These meteors are nice and slow with a velocity
of about 25 km per second, so although few and far between, these are
wonderful meteors to see.

The southern iota Aquarids (SIA) reach a maximum on August 4th, with a
radiant at 334 degrees, ie RA 22h 16.2m, Dec -15, which is about 6 degrees
off to the left of the star delta Capricornus, the top left star of the
triangle of Capricornus. ZHR rates will be about 2 meteors per
hour. These are average velocity meteors, at about 34 km per second, and
can be seen until about August 15th.

The northern delta Aquarids (NDA) reach a maximum on August 8th, with a
radiant at 335 degrees, ie RA 22h 19.8m, Dec -05, which is about 4 degrees
south of the star gamma Aquarius. These are average velocity meteors, at
about 42 km per second, and the ZHR rate at maximum is about 4 meteors per
hour. They can be seen up until about August 25th.

The kappa Cygnids (KCG) reach a maximum on August 17th, but can be seen
from about August 3rd until the 25th. At maximum on the 17th, the radiant
will be at 286 degrees, ie RA 19h 4.2m, Dec +59, which is about 9 degrees
south of the star delta Draco, also known as Nodus Secundus, the "second
knot" or "he-goat." Apparently, the ancients believed that when a comet was
visible in this area of Draco, poison was scattered all over the world
- yet another old comet tale! Kappa Cygnids are slow meteors, at about 25
km per second, so will be quite distinctive. At maximum, ZHR rates will
reach about 3 meteors per hour. According to the IMO, "occasional slow
fireballs from this source have been reported... There has been some
suggestion of a variation in its activity at times, perhaps coupled with a
periodicity in fireball sightings, but more data are urgently needed on a
shower that is often ignored in favor of the Perseids during August."

The northern iota Aquarids (NIA) reach a maximum several days later, on
August 19th, and can be seen from about August 11th to 31st. At maximum on
the 19th, the radiant will be at 327 degrees, ie RA 21h 48m, Dec -06, which
is about 4 degrees to the left of the star beta Aquarius, the star
Sadalsuud. These are almost slow meteors, at about 31 km per second. At
maximum, ZHR rates will reach about 3 meteors per hour. The IMO suggests
that highest rates could occur several days past the suspected peak.

The alpha Aurigids (AUR) start in the last week of the month, although
won't reach a maximum until September 1st, at which time the radiant will
be at 084 degrees, ie RA 5h 36m, Dec +42, which is about 5 degrees to the
left of the star eta Auriga, the star known as Hoedus II, "the Charioteer's
2nd kid goat." These are fast meteors, at 66 km per second, and at maximum
will reach rates of about 10 meteors per hour - very good for a minor
shower!

Besides recognized showers, there is also sporadic meteor activity in
August, about 7 meteors per hour, visible to the unaided eye. This
activity is comprised partly of random meteor activity and partly of meteors
that belong to long-ago, now untraceable showers.

Full moon this month is on Saturday August 4th, last quarter on Sunday
August 12th, new moon on Sunday August 19th, and first quarter on Saturday
August 25th. This month, Mars is getting very low in the evening sky for
northern observers, at magnitude -1.3 at mid-month.

The morning sky is filling up with planets though! Venus is the brightest,
at magnitude -4.0, and makes a nice reference for bright Perseid meteors in
the morning sky. Saturn is in Taurus, and will stand about 35 degrees
above the eastern horizon at the beginning of morning twilight, at
magnitude -0.3. Jupiter is in Gemini, and by the end of the month, for
northern observers, will be about 45 degrees above the eastern horizon at
the beginning of morning twilight, at a respectable magnitude -2.1.

There are a number of nice planetary configurations in August. Even if you
can't catch the planets at the exact times noted, they will still be fairly
close when you are out observing. Venus will be very close to Jupiter in
the sky on August 6th at 0 hours UT, and very close to the moon on August
16th at 13 hours UT. Saturn will be very close to the moon (0.2 degrees)
on August 14th at 3 hours UT, and will be occulted if you live in south and
east Africa, India, southern China, or Indonesia. Jupiter will be very
close to the moon (0.4 degrees) on August 15th at 20 hours UT, and will be
occulted if you live in southwest Canada, the United States, Alaska,
eastern China, and Japan.

For information on what to record while meteor observing - if you would
like to make observations useful to meteor researchers - check out our NAMN
Observing Guide at http://web.infoavedot net/~meteorobs/guide.html. The
information we keep track of is actually fairly basic - the time of each
meteor, its brightness, its speed (ie. slow, average, fast), what shower it
belongs to, and any other characteristics, such as color, or train left
behind.

August is a great time of year for meteor observing. It's warm, and the
showers are plentiful. If you are new, and just want to relax and take in
the meteor show, enjoy! If you want to try recording some meteor data,
then check out our observing guide, and drop a note to our NAMN Coordinator
at MeteorObs@charlestondot net if you have any questions. But get outside and
enjoy the meteors of August, one of the many wonders of our night sky!


3. Recent Observations...

As the meteor activity began to pick up in June, so did the number of
observers and reports sent to NAMN. During the month, we received
observations from 22 observers providing coverage of 15 different nights in
June, as well as a few more reports for April and May. Our thanks go to
the following observers who submitted reports:

Karl Antier, France           Roberto Haver, Italy
Jure Atanackov, Slovenia      Javor Kac, Slovenia
Dustin Brown, USA             Robert Lunsford, USA
Ed Cannon, USA                Pierre Martin, Canada
Mark Davis, USA               Francisco Ocana, Spain
Sid Ferreira, USA             Catrin Reulbach, Switzerland
Mark Fox, USA                 James Smith, Germany, Switzerland
Robert Gardner, USA           Attila Szalai, Hungary
Lew Gramer, USA               Michel Vandeputte, Belgium
Robin Gray, USA               Roger Venable, USA
Cathy Hall, Canada            Harry Waldron, USA

We issued a special call for observations for the June Bootids. This
shower normally produces little activity, but does show some erratic
behavior. In 1998, there was an unexpected display in which the ZHR reached
from 50 to over 100 meteors per hour. That was not what happened this year.
Nine observers participated in the campaign held over the nights of June
26th and 27th. These included Karl Antier, Ed Cannon, Mark Davis, Mark Fox,
Lew Gramer, Robin Gray, Roberto Haver, Pierre Martin, and James Smith.
Activity from the June Bootid radiant was limited as only five observers
(Lew Gramer, Robin Gray, Roberto Haver, Pierre Martin, James Smith)
reporting any at all during the entire month (see observations below).

The bulk of reported shower activity came from several minor showers active
this time of year. Below is listed the shower, number of meteors observed,
and the observers who reported them:

Chi Scorpiids (2) ­ James Smith, Attila Szalai; June Lyrids (20) - Cathy
Hall, Robert Lunsford, Pierre Martin, Attila Szalai, Michel Vandeputte;
Sagittarids (46) - Karl Antier, Mark Davis, Lew Gramer, Cathy Hall, Roberto
Haver, Javor Kac, Robert Lunsford, Pierre Martin; Theta Ophiuchids (6) ­
Roberto Haver, Pierre Martin; and Xi Draconids (16) ­ Robert Gardner, Robert
Lunsford, Pierre Martin, Michel Vandeputte

Below is a listing of all the observations received during June:

April 21/22:
Roger Venable, USA (Teff=3.02, 23 Lyrids, 18 sporadics)

May 3/4:
James Smith, Switzerland (Teff=1.25, 1 sporadic)

May 9/10:
Catrin Reulbach, Switzerland (Teff=0.50, 2 sporadics); James Smith,
Switzerland (Teff=0.50, 2 sporadics)

May 11/12:
Catrin Reulbach, Switzerland (Teff=1.50, 3 alpha Bootids, 3 sporadics);
James Smith, Switzerland (Teff=1.50, 3 alpha Bootids, 1 Ophiuchid, 3
sporadics)

May 12/13:
Catrin Reulbach, Switzerland (Teff=1.00, 7 sporadics); James Smith,
Switzerland (Teff=1.00, 7 sporadics)

June 11/12:
Robert Lunsford, USA (Teff=1.00, 2 June Lyrids, 2 Sagittarids, 1 xi
Draconid, 3 sporadics); Pierre Martin, Canada (Teff=1.04, 2 June Lyrids, 1
Sagittarid, 2 xi Draconids, 4 sporadics)

June 12/13:
Robert Gardner, USA (Teff=1.92, 1 xi Draconid, 2 sporadics); Pierre Martin,
Canada (Teff=2.29, 1 June Lyrid, 2 Sagittarids, 1 theta Ophiuchid, 1 xi
Draconid, 11 sporadics)

June 13/14:
Pierre Martin, Canada (Teff=2.48, 4 June Lyrids, 4 Sagittarids, 1 theta
Ophiuchid, 3 xi Draconids, 11 sporadics)

June 14/15:
Sid Ferreira, USA (Teff=?, 2 sporadics); Pierre Martin, Canada (Teff=2.86, 2
June Lyrids, 3 Sagittarids, 2 xi Draconids, 15 sporadics); Francisco Ocana,
Spain (Teff=1.00, 3 sporadics)

June 15/16:
Cathy Hall, Canada (Teff=3.92, 2 June Lyrids, 1 Sagittarid, 11 sporadics);
Pierre Martin, Canada (Teff=3.00, 1 June Lyrid, 1 Sagittarid, 3 xi
Draconids, 16 sporadics); Francisco Ocana, Spain (Teff=1.00, no meteors);
Attila Szalai, Hungary (Teff=1.50, 1 chi Scorpiid, 2 June Lyrids, 1
sporadic); Michel Vandeputte, Belgium (Teff=1.97, 2 June Lyrids, 2 xi
Draconids, 8 sporadics)

June 16/17:
Attila Szalai, Hungary (Teff=1.00, 1 June Lyrid, 1 sporadic)

June 17/18:
Pierre Martin, Canada (Teff=2.12, 1 June Lyrid, 2 Sagittarids, 1 xi
Draconid, 8 sporadics)

June 19/20:
Karl Antier, France (Teff=1.22, 10 sporadics)

June 20/21:
Karl Antier, France (Teff=1.20, 1 Sagittarid, 6 sporadics)

June 23/24:
Roberto Haver, Italy (Teff=2.64, 2 June Bootids, 8 Sagittarids, 23
sporadics); Javor Kac, Slovenia (Teff=1.37, 2 Sagittarids, 13 sporadics)

June 24/25:
Javor Kac, Slovenia (Teff=2.05, 2 Sagittarids, 13 sporadics); Pierre Martin,
Canada (Teff=1.85, 1 June Bootid, 2 Sagittarids, 1 theta Ophiuchid, 13
sporadics); James Smith, Germany (Teff=1.00, 1 chi Scorpiid)

June 25/26:
Karl Antier, France (Teff=1.02, 9 sporadics); Lew Gramer, USA (Teff=1.00, 1
June Bootid, 1 Sagittarid, 8 sporadics); Robin Gray, USA (Teff=0.61, 14
sporadics); Pierre Martin, Canada (Teff=2.02, 2 Sagittarids, 2 theta
Ophiuchids, 16 sporadics)

June 26/27:
Ed Cannon, USA (Teff=1.03, 8 sporadics); Mark Davis, USA (Teff=2.33, 1
Sagittarid, 13 sporadics); Mark Fox, USA (Teff=1.01, 1 sporadic); Roberto
Haver, Italy (Teff=2.57, 5 June Bootids, 3 Sagittarids, 1 theta Ophiuchid,
30 sporadics); Pierre Martin, Canada (Teff=4.29, 1 June Bootid, 2
Sagittarids, 24 sporadics); James Smith, Germany (Teff=1.00, 1 June Bootid,
2 sporadics)

June 27/28:
Karl Antier, France (Teff=0.98, 18 sporadics); Jure Atanackov, Slovenia
(Teff=0.50, 3 sporadics); Lew Gramer, USA (Teff=1.33, 1 June Bootid, 6
Sagittarids, 11 sporadics); Robin Gray, USA (Teff=1.00, 1 June Bootid, 23
sporadics)

June 28/29:
Robin Gray, USA (Teff=1.03, 17 sporadics)


4. Upcoming Meetings...

August 6-10, 2001 - Sweden:
The Meteoroids 2001 conference will be held at the Swedish Institute of
Space Physics in Kiruna, Sweden. Topics covered will include historical
observations and perspectives on meteoroids; dynamics, sources and
spatial distribution; detection and characteristics of meteoroids from
interstellar space; the meteoroid interaction process in the atmosphere;
hypervelocity impact effects on spacecraft; Leonid meteor storms;
optical observations of meteors; and meteor radar work. For
information, contact Asta Pellinen-Wannberg at
asta.pellinen-wannberg@irf.se and check out the website at
http://www.irf.se/Meteoroids2001.

September 20-23, 2001 - Slovenia:
IMC 2001, the worldwide meeting for meteor observers of the
International Meteor Organization, will be held this year in the town of
Cerkno, in Slovenia. This is a convention for both amateurs and
professionals. For North Americans not familiar with the map, Slovenia
is on the Adriatic Sea, east of Venice and south of Austria. It is
within driving distance of major European cities. This is a great
opportunity to meet and chat with observers from all over the globe -
and a wonderful excuse to visit Europe as well! Come join us! Details can
be found on the IMO website at http://www.imodot net.


5. For more info...

Contact:
Mark Davis, MeteorObs@charlestondot net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network

And check out:
NAMN home page:
http://web.infoavedot net/~meteorobs

Back issues of NAMN Notes can be found on-line at the NAMN website, and
in the meteorobs archives at:
http://www.tiacdot net/users/lewkaren/meteorobs
by selecting 'Browse Archive by Month'

To subscribe to the meteor email list or
To find out information on our weekly chat sessions:
Contact Lew Gramer at:
dedalus@alum.mitdot edu

============================================

Here's to 'Clear Skies' for August...

August 2001 NAMN Notes co-written
by Mark Davis and Cathy Hall

============================================



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