(meteorobs) NAMN Notes: April 2008

[meteors at comcast.net]

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NAMN Notes: April 2008
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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://www.namnmeteors.org

Contents:

1. Challenging Lyrids for 2008...
2. A Southern Shower peeking above the Horizon (PPU)...
3. The eta-Aquarids (ETA) Compete with Dawn and the Moon...
4. Ecliptic (ANT) meteors for April...
5. Targets for Plotting...
6. The Meteor Moonth...
7. Index to 2006 Articles...
8. For More Information…


1. Challenging Lyrids for 2008...

The moon is in about the worst possible position for this year’s Lyrids.
So it will be a challenge to collect quality data. I hope to be able to
help you get the most out of whatever time you can contribute.

First, the bad news. The moon is full on April 20th, only a day and a
half before the Lyrid peak. This means the 97% illuminated moon will be
rising in the ESE at about the same time the Lyrid radiant is rising in
the northeast. They will only be separated by about 75 degrees. So it
will be a battle all night long.

The International Meteor Organization (IMO) predicts the peak will occur
between 21h UT on the 21st and 08h UT on the 22nd.  Based on last years
peak (IMO ZHR 21 +/-3 at Solar Longitude 32.34) this would be the 08h UT
time on the 22nd. In addition, last year, two North American observers
detected a short possible second peak (EZHR 34 +/- 13) at Solar
Longitude 32.63; this would be about 1230h UT on the 22nd this year.
Some far western US sites might be able to see this, should it return,
as well as Hawaiian locations.

So how do we get the most out of these circumstances?

First, hope for very clear and dry weather. Even a small bit of haze in
the air can be devastating with a full moon. Second, you must find a way
to block the moon, and place it behind you as much as possible. The good
news (yes a tiny bit of good news) is that the moon rides fairly low
across the sky this night. It only reaches an elevation of 25 degrees at
41 N, only 35 degrees at 30 N at transit ~ 2 AM daylight time. So you
should be able to block it. You can use a building, a car, or even a
beach umbrella, but hide that thing!

Unfortunately, since the separation between moon and radiant is only 75
degrees, you don’t want to look too near the radiant; place your field
of view on the other side. A field centered between Draco’s head and the
bowl of the little dipper is about 40 degrees from the radiant, but
nearly 120 degrees from the moon. That’s the best advice I can give.
Good luck to all.

Lyrids (LYR) Meteor Velocity: 49 km/sec (medium fast)
Start of Activity  - April 15: Radiant RA 263 (17:32), Dec +34
Peak of Activity - April 22: Radiant RA 271 (18:04), Dec +34
End of Activity - April 25: Radiant RA 274 (18:16), Dec +34


2. A Southern Shower peeking above the Horizon (PPU)...

Challenged by both the moon and it’s far southern radiant, the
pi-Puppids are active during the same time as the Lyrids. However, they
are much harder to see. The radiant transits around 6PM daylight time,
well before sunset, and by the time it gets dark is only 10-20 degrees
above the SSW horizon as it continues to sink. This shower should
probably be called the sigma Puppids, since the radiant is closer to
that star than it is to pi. These are very slow meteors, so should
really stand out, and might be glimpsed before the moon rises. There are
reports (see meteorobs discussions) of some enhancement this year, but
that occurs before sunset across North America. No NAMN observers have
reported any during the last 4 years, which shows how difficult they can
be. Perhaps we can break that streak this year. Might give you something
to do while waiting for the Lyrid radiant to rise!

Pi Puppids (PPU): Meteor Velocity 18 km/sec (very slow)
Start of Activity - April 15: Radiant RA 106 (07:04), Dec -44
Peak of Activity - April 22-23: Radiant RA 110 (07:20), Dec -45
End of Activity - April 28: Radiant RA 112 (07:29), Dec -45


3. The eta-Aquarids (ETA) Compete with Dawn and the Moon...

After mid month, the eta Aquarids begin showing up in the predawn hours.
This is one of two showers displaying the debris from Halley’s Comet,
the other being October’s Orionids. Through the month of April, the moon
will be up as the radiant rises in the eastern sky, fortunately by the
time of the peak on May 5, it will be a New Moon. On April 20th, the
radiant rises about 3AM and just reaches 30 degree elevation by
twilight. By the end of the month, the crescent moon and radiant will be
right next to each other, rising about 2:30 AM. We’ll cover this shower
in more detail next month.

Eta Aquarids (ETA): Meteor Velocity 66 km/sec (very fast)
Start of Activity - April 19: Radiant RA 322 (21:28), Dec -08
End of Month - April 30: Radiant RA 332 (22:08), Dec -03


4. Ecliptic (ANT) Meteors for April...

The wide antihelion (ANT) radiant continues it’s daily trek across the
sky, this month moving from near Spica in Virgo at the beginning of the
month through Libra by the end. Remember the ANT radiant should be
assumed to be 30 degrees wide along the ecliptic and 7 ½ degrees above
and below it. It consists of many weak showers that have been smeared
out by interactions with the planets along the ecliptic, and are
generally too diffuse to identify individually. In past years these were
called the Virginids. Sirko Molau’s analysis of IMO video data suggests
some enhancements in activity around the 8th, 19th, and 23rd; the last
two will be wiped out by the Full Moon. These have highest rates an hour
or two after midnight.

Antihelion Radiant (ANT): Meteor Velocity 29-37 km/sec (medium speed)
Start of Month - April 1: Radiant RA 204 (13:36), Dec -10
New Moon - April 6: Radiant RA 209 (13:56), Dec -11
Last night with a moon free hour - April 15: RA 218 (14:32), Dec -15
Full Moon - April 20
First night with moon free hour - April 23: Radiant RA 225 (15:00), Dec -17
End of Month - April 30: Radiant RA 232 (15:28), Dec -19


5. Targets for Plotting...

Sirko Molau’s analysis of IMO video data has revealed two very low rate
showers that you might want to keep an eye out for. Both of these have
rates so low that there’s a great danger in attributing sporadics to
these sources, so it is suggested that only experienced observers who
can accurately estimate angular velocity even attempt to report these.
You must then use that information to see if it is a speed appropriate
for the shower. Plotting is preferred (or photographic or video data) to
confirm the radiant. See the IMO shower calendar mentioned below for how
to convert radiant elevation and shower velocity to expected angular speeds.

The first is a radiant very near Vega at the end of March and beginning
of April. For the time being, we can call this radiant MAL. This stands
for March-April Lyrids or March alpha Lyrids. The velocity is 41 km/sec.
Again, rates are expected to be quite low.

SM shower 2 (N Toroidal - MAL): Meteor Velocity 41 km/sec (Medium fast)
Start of Activity - March 30: Radiant RA 276 (18:24), Dec +41
Peak of Activity - March 31: Radiant RA 276 (18:25), Dec +41
End of Activity - April 7: Radiant RA 277 (18:28), Dec +37

The second has a radiant in Draco, near the handle of the Big Dipper.
These are exceptionally slow meteors, so could be easy to pick out. For
the time being, we will call this radiant APD, for April Draconids.

SM shower 3 (April Draconids - APD): Meteor Velocity 18 km/sec
Start of Activity - March 31: Radiant RA 213 (14:11), Dec +62
Peak/End of Activity - April 6: Radiant RA 202 (13:28), Dec +64

Finally, a word about the names of these minor showers. When there is
confirmation of a shower’s existence, I search the old IMO working list,
the IAU shower list, and several other sources. If no name is found, we
assign a temporary name. Most of these showers will receive an official
name and 3 letter codes from the IMO and IAU at the next IAU General
Assembly in 2009. At that time we can consolidate the records to reflect
the official name. That’s why I use the phrase “for the time being”.


6. The Meteor Moonth...

The month begins with a thin crescent moon rising just before twilight
in the morning, with the New Moon on the 6th. Basically, the first 8 or
9 days are a moon free period. After that, the waxing moon sets later
each night until by the 15th or so there’s only an hour left between
moonset and twilight. From the 16th to 22nd the near Full moon (Full on
the 20th) will be up all hours of darkness. Beginning around the 23rd
there’s a moon free hour in the evening, which increases every night as
it rises later every day. By the morning of the 26th there is some time
after 1 AM (which is really midnight) before the moon comes up, and by
the end of the month the crescent moon will rise an hour or two before dawn.

The brightest planet this month is Jupiter, rising in the early morning
hours in Sagittarius. It brightens from Magnitude -2.2 to -2.4 during
the month.

Saturn and Mars are up most of the night. Saturn is in Leo near the +1.4
star Regulus, and dims slightly from magnitude +0.4 to +0.5 during the
month. Mars is in Gemini, near Pollux (+1.2) and Castor (+1.6) and dims
rapidly from +0.9 to +1.2.

Some other stars you can use as a reference that are up most of the
night are Spica, near the ANT radiant at magnitude +1.0 and Arcturus in
Bootes at magnitude 0. To the left of Arcturus are two stars of +4.5 and
+3.8, to the right, three of +2.7, +4.5, and +4.0. As Scorpio comes into
view, the three brightest in a line on the right are +2.6, +1.9, and
+2.8 from top to bottom.


7. Index to 2006 Articles...

January 2007
Happy New Year!...
Quadrantids, Highlight for January...
Other January Meteor Activity...
Index to 2006 Articles...

February 2007
Of Transient Phenomena and Comet McNaught...
February Meteors for Winter Nights...

March 2007
Meteor Activity for March...
Other March Sky Activity...
International Meteor Conference...

April 2007
Lyrids - Our Spring Shower...
Other April Meteor Activity...
International Astronomy Day...

May 2007
Eta Aquarids - Comet Halley and the Meteors...
Watching the Birth of a New Meteor Shower - by G.W. Gliba...
Other May Meteor Activity...

June 2007
June and the Bootid Meteors...
Other June Meteor Activity...
Lyrids Put on Good Show for a Lonely Observer... by Wayne T. Hally
Astronomical Info Sheets...

July 2007
Time Passages and Meteor Friends...
Aquarids for the Summertime...
Other July Meteor Activity...

August 2007
Perseids - Highlight of the Summer...
Other Summer Meteor Activity...

September 2007
A Change for NAMN...
September - alpha Aurigids...
Other September Meteor Activity...

October 2007
Great Thanks and Hello...
Summer Results...
October Highlight - The Orionids...
Other October Meteor Activity...
Meteor Science Corner...

November 2007
Orionids Come Back Strong in 2007...
Orionids and Taurids Continue in November...
Discrimination of Close Radiants...
A Good Year for Watching Leonids, but...
Other November Activity...

December 2007
Highlight of the Month/Year: The Geminids...
Other Major and Minor Showers of December...
Antihelion Radiant Returns...
COM and MON Expanded Discussion...
Don’t Miss the Quadrantids...


8. For More Information...

For radiant positions and more detailed descriptions of showers, see the
IMO 2008 Meteor Shower Calendar at:  http://www.imo.net/calendar/2008

You will need to use the 2007 calendar to see radiant position charts
for the Lyrids and PPU, since they don’t show the chart for full moon
years. The positions are accurate enough for this year.

Feel free to contact us for questions and comments!!
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NAMN email: namn at namnmeteors.org
NAMN website: http://www.namnmeteors.org

Mark Davis, meteors at comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network

Wayne T Hally, meteoreye at comcast.net
High Bridge NJ
Writer, NAMN Notes

Lew Gramer, dedalus at alum.mit.edu
Homestead, Florida, USA
Coordinator, Public Outreach
Owner/Moderator, 'MeteorObs'

Kevin Kilkenny, namnfireball at earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites

Back issues of NAMN Notes can be found online at the NAMN website and in
the MeteorObs archives at:
http://www.meteorobs.org by selecting 'Browse Archive by Month'

To subscribe to the meteor email list:
Contact Lew Gramer at: dedalus at alum.mit.edu

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

April 2008 NAMN Notes
Written by Wayne T. Hally & edited by Mark Davis
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