[Prev][Next][Index][Thread]
(meteorobs) FW: BOUNCE meteorobs@jovian.com: Non-member submission from [Robert Verish <bolidechaser@yahoo.com>]
Note to listmembers:
Please note that Bo* :-) is not a member of meteorobs, so if you wish to
reply, please replace the meteorobs "reply" with his address. I also
included what he had forwarded from Ron Ballke...although Ron usually posts
the message to meteorobs, for some reason he didn't this time
Elf Wayne
----------
Date: Wed, 11 Aug 1999 11:29:35 -0700 (PDT)
From: Robert Verish <bolidechaser@yahoo.com>
Subject: Re: Here Come The Perseids!
To: meteorite-list@meteoritecentral.com
Cc: meteorobs@jovian.com, astro@store-forward.mindspring.com,
ruizj01@Pacesetter.COM
Hello List,
I'm leading a group of meteor watchers up to Mt Gleason, here in
Southern California, on Thursday night. It's remarkable how much
confusion there is about the various "peaks" and the prime viewing
times. Largely stems from Griffith Observatory's Sky Report telling
people that "it peaks on the
morning[sic] of Thursday, August 12"??!
I've double checked this, and for us here in So. Cal. these are the
predicted peaks:
1st peak - 21-23hr.UT 12Aug99 - or 13-15hr. PDT (or 3PM the 12th!)
2nd peak - 04-06hr.UT 13Aug99 - or 20-22hr. PDT (or 9PM the 12th!)
3rd peak - 13-15hr.UT 13Aug99 - or 05-07hr. PDT (or 6AM the 13th!)
(Now I see why the viewing will be so much better on the U.S. East
Coast |-(
The "3rd peak" is very "iffy" because it was only first observed in
1997. But this would make anybody's meteor count during that period of
time even that more important. Heads up Hawaii!
Anyway, here in LA County, feel free to join us at Mt Gleason (on the
12/13TH) or join the group going to Mt Wilson. Wherever you're
located, should you see a fireball, you can contact the Mt. Gleason
observation team on our cell phone (818) 437-4926, and we can compare
notes.
My information was obtained from the following web pages:
http://www.imodot net/calendar/cal99.html#Perseids
and
http://science.nasadot gov/newhome/headlines/ast09aug99_1.htm
Bo*
--- Ron Baalke <BAALKE@kelvin.jpl.nasadot gov> wrote:
>
> Here come the Perseids!
> Marshall Space Flight Center
> http://science.nasadot gov/newhome/headlines/ast09aug99_1.htm
>
> The 1999 Perseid meteor shower peaks on August 12th
> and 13th under the dark
> skies of a nearly new moon.
>
> August 9, 1999: The attention of the world will be
> riveted on the heavens
> this week as the last total solar eclipse of the
> 20th century takes place on
> August 11. However, for most skywatchers outside the
> path of totality, the
> best sky show won't occur until a day and a half
> later, on Thursday, August
> 12, and Friday, August 13. That's when the annual
> Perseid meteor shower
> reaches its peak with 50 to 150 shooting stars per
> hour.
>
> In recent years the spectacular Leonid meteors have
> attracted considerable
> attention, but historically the Perseids are the
> best known of all meteor
> showers. It rarely fails to provide a pleasing
> display and, because of its
> summertime appearance, it tends to attract many
> astronomy novices.
>
> This year should be a good one for viewing Perseids.
> The shower's maximum
> takes place on August 12, 1999, under dark skies
> just one day after the new
> moon. Although the Perseids officially begin in late
> July, the shower builds
> rather slowly in intensity until there is a series
> of sharp peaks in
> activity near mid-August.
>
> The figure below shows the expected activity profile
> for 1999 based on
> observations in 1997. The shower's maximum is
> centered around 21 UT (2 p.m.
> PDT) on Thursday, August 12, 1999. The level of
> activity remains relatively
> high for nearly 24 hours afterward, so the early
> morning hours before dawn
> on Thursday, August 12 and on Friday, August 13
> should be good times to
> observe in most places [click for more observing
> tips]. The other two times
> indicated in the figure (0700 UT on August 12 and
> August 13) are launch
> windows for the Science@NASA Perseids Live! high
> altitude balloon flight
> which will transmit a live webcast of the meteor
> shower from the
> stratosphere.
>
> Like most meteor showers, the Perseids are caused by
> comet debris. As comets
> enter the inner solar system, they are warmed by the
> sun and peppered by the
> solar wind, which produces the familar tails that
> stretch across the night
> sky when a bright comet is close to Earth. Comet
> tails are made of tiny
> pieces of ice, dust, and rock which are spewed into
> interplanetary space as
> they bubble off the comet's nucleus. When Earth
> encounters these particles
> on its journey around the Sun, they strike the
> atmosphere speeds exceeding
> 100,000 mph. (The average speed of Perseid
> meteoroids is 130,000 mph!) Most
> are observed as a bright streak across the sky that
> can last for several
> seconds, but occasionally a large fragment will
> explode in a multicolored
> fireball. Most of the streaks (popularly called
> 'shooting stars') are caused
> by meteoroids about the size of a grain of sand, but
> much less dense.
> Although they travel at high speeds, these tiny
> meteoroids pose no threat to
> people or objects on the ground.
>
> The Perseids were the first meteors ever associated
> with a particular comet.
> From 1861 to 1863, observers noted a great increase
> in the number of August
> Perseids. As many as 215 per hour were seen in 1983.
> The Italian astronomer
> Giovanni Virginio Schiaparelli (better known for
> giving the name "canali,"
> or "channels," to the dark linear markings on Mars)
> calculated the orbits of
> some Perseid meteoroids and discovered that they
> closely matched that of
> periodic comet Swift-Tuttle, which had been
> discovered in 1862 during its
> close approach to Earth. Swift-Tuttle orbits the Sun
> once every 135 years.
> The last time it passed near Earth was in December
> 1992. The proximity of
> the comet once again caused an increase in Perseid
> activity and, in August
> 1993, observers in Central Europe were treated to
> 200 to 500 meteors per
> hour. Swift-Tuttle won't make another swing through
> the inner solar system
> until 2126, but when it does the comet itself is
> expected to be an
> impressive sight as seen from Earth, rivalling Comet
> Hyakutake in 1996 or
> Comet Hale-Bopp in 1997.
>
> Perseid observing tips
>
> Perseid meteors can be seen anytime after the sun
> has set and the
> constellation Perseus is above the horizon (which is
> nearly all the time
> from observing sites in the northern hemisphere). In
> practice, watching for
> meteors between sunset and midnight is rarely
> profitable. The best time to
> look is between about 2 a.m. and dawn. That's when
> the local sky is pointing
> directly into the meteoroid debris stream (see the
> diagram below). The early
> morning hours of August 12 and August 13 should be
> good times to watch if
> you live in the northern hemisphere.
>
> For northern hemisphere observers at latitudes
> higher than about 35 degrees
> Perseus is circumpolar -- it is always above the
> horizon. Unfortunately, due
> to the high declination of the radiant, the Perseids
> are not a good shower
> for skywatchers south of the equator.
>
> The sky map below represents a view of the sky
> looking northeast from a
> mid-latitude viewing site at 3:00 a.m. (local time
> wherever you live). The
> radiant, in the constellation Perseus, is located
> almost midway between
> Jupiter in the east and Polaris in the north.
> Jupiter (magnitude -2.6) and
> Saturn (magnitude +0.3) will be very bright and easy
> to spot.
>
> Experienced observers suggest the following viewing
> stategy: Bring a
> reclining chair, or spread a thick blanket over a
> flat spot of ground. Lie
> down and look up somewhat toward the north. You
> don't need to stare directly
> at the radiant -- the meteors can appear anywhere in
> the sky. Their trails
> will tend to point back toward the radiant, pictured
> as a red dot in the sky
> map below. Binoculars and telescopes are not
> essential. The naked eye is
> usually best for seeing meteors which often streak
> more than 45 degrees
> across the sky. The field of view of most binoculars
> and telescopes is
> simply too narrow for good meteor observations.
To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html