(meteorobs) Possible ACG photo's.

[stange]

Wayne, Mark,

Not good at this at all, but a back-azimuth(radiant?) of two meteors "seems" 
to come between Deneb & Lacerta off of the Cygnus tail TOWARD the mid 
section of Ursa Minors tail on two different consecutive nights at nearly 
the same times.

Date/time photo titles are PDT  mmddhhmm
My Sentinel location 39 7.208  121 38.363 Northern California.

http://www.geocities.com/stange34@sbcglobal.net/07020141

http://www.geocities.com/stange34@sbcglobal.net/07010129

YCSentinel







----- Original Message ----- 
From: <meteors at comcast.net>
To: "MeteorObs" <meteorobs at meteorobs.org>
Sent: 2008/07/02 15:26
Subject: (meteorobs) NAMN Notes: July 2008


**************************
NAMN Notes: July 2008
**************************

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. July’s Southern Showers...
2. The Perseids Perk Up...
3. A Multitude of Minor Showers...
4. Magnitude References...
5. For More Information...


1. July’s Southern Showers...

As meteor rates begin to pick up in the late summer, a number of showers
become active in the area surrounding the Antihelion (ANT) radiant. The
alpha-Capricornids (CAP) overlap with the Antihelions on the western
edge, but stand out due to their slow velocity. South of the ANT, the
Southern delta-Aquarids (SDA) and Piscis Austrinids (PAU) also peak
toward the end of the month. All of these showers provide low rates for
northern hemisphere observers, due to their low elevation at this hazy
time of the year.

The highest ZHR (~20) is owned by the SDAs - the NAMN has recorded about
270 per year recently. The CAP’s ZHR is only 3 but since it’s radiant is
about 6 degrees higher, comparable to the Antihelions, just over a
hundred of each (ANT and CAP) are seen each July. Finally the PAU
radiant, much lower than the others (nearly 20 degrees below the CAP
radiant) are rare events in North America, averaging only 8 meteors per
year.

With all these radiants packed so close together, this is a good time to
break out an alignment cord to help separate the shower members. For
those not familiar with the technique, all you need is a string or cord
long enough to be held between your outstretched arms. When you see a
meteor, you then place the cord over the path with one end held over the
intersection of all these radiants. Once you get the hang of it, this
allows you to clearly differentiate meteors from shower radiants only a
few degrees apart.

It’s good practice as well for later in the year when the Northern and
Southern Taurids are close to each other, as well as in December when
there are several showers near the Geminids. Once you practice it a bit,
it only takes a second or two to align the cord and trace back to the
southern shower radiants. The benefit to meteor data is that instead of
just counting the Aquarids as a whole, accurate data is collected for
each of the individual showers.

Another tool to tell them apart is the speed. The SDAs are the fastest
at 41 km/sec, while PAUs are 35, the Antihelions about 30, and the CAP
meteors slowest at 23 km/sec. In the case where the alignment cord
points at two or three radiants, if you’ve seen enough of them, you
should be able to tell which shower the meteor came from based on the
angular velocity

Of course, in the midst of these showers, the ANTihelion radiant
continues on it’s eastward march at about a degree per day. In past
years this included the Northern delta-Aquarids and Northern and
Southern iota-Aquarids. All these showers had rates at or below the
visual detection threshold and are within the ANT radiant, which is 15
degrees from north to south, and 30 degrees wide from east to west along
the ecliptic. They should be reported to the IMO and NAMN as ANT meteors.

For all the showers, with the full moon on the 18th, I give positions on
the 15th and 22nd when there is more than an hour of dark sky time: in
the morning on the 15th, in the evening for the 22nd. Some locations may
be able to get a full dark hour one day closer to the full moon. For
days in between those listed you can interpolate, or contact me for an
Excel spreadsheet with daily positions for all showers.

Antihelion (ANT) 30 km/sec
Date      Position RA (degrees, then Hr:min), Declination
July 1:   RA 292 (19:28), Dec -21
July 8:   RA 298 (19:54), Dec -19
July 15:  RA 305 (20:20), Dec -18
July 22:  RA 312 (20:48), Dec -16
July 31:  RA 320 (21:20), Dec -14

Alpha Capricornids (CAP) 23 km/sec
Date     Position RA (degrees, then Hr:min), Declination
July 3:  RA 283 (18:54), Dec -16   IMO Start of activity
July 8:  RA 287 (19:06), Dec -16
July 15: RA 292 (19:29), Dec -14
July 22: RA 299 (19:54), Dec -12
July 30: RA 305 (20:20), Dec -10   IMO Peak

Southern delta Aquarids (SDA) 41 km/sec
Date     Position RA (degrees, then Hr:min), Declination
July 12: RA 327 (21:46), Dec -19 IMO Start of activity
July 22: RA 335 (22:18), Dec -18
July 31: RA 341 (22:43), Dec -16 Peak July 28-31

Piscis Austrinids (PAU) 35 km/sec
Date      Position RA (degrees, then Hr:min), Declination
July 15:  RA 330 (22:00), Dec -34 IMO Start of activity
July 22:  RA 336 (22:22), Dec -32
July 28:  RA 341 (22:44), Dec -30 Peak

There is one other item of note in this area. Sirko Molau’s IMO video
data summary shows another short lived radiant from July 29th to August
3rd. It may be related to the CAP stream, since the meteors have similar
speed (a bit slower) and is nearby. The radiant is located at RA 298
(19:50) and Dec -04, in southern Aquila. If you see any of these, for
this year at least, report them as SAQ.


2. The Perseids Perk Up...

This most popular shower for the public and casual observer begins in
mid July. While this year the peak in August will be squeezed by the
Full Moon, as the rates slowly rise during late July we have an
opportunity to collect some good data. Some care must be taken to use
the correct radiant for any date you observe though. During July the
radiant is moving more than a degree per day through Cassiopeia into
Perseus. IMO video data suggests a start date as early as July 12th, so
I will use that as my start date in the list below.

The Perseids are of course material from the comet 109P/Swift Tuttle,
and we’ll discuss them more next month as we approach the August 12th
peak. The important thing for July is that these meteoroids hit us much
closer to head-on than any of the southern showers so traverse the sky
much faster. This also leads to brighter meteors in general.

There are a few days from that start date before the Full Moon, and once
skies darken again in the third week of July there should be more than
one or two Perseids per hour. By the end of the month, they should
become the most active source of meteors in the sky.

Perseids (PER) 59 km/sec
Date     Position RA (degrees, then Hr:min), Declination
July 12: RA 000 (0:00), Dec +51 Start of activity? In Cassiopeia
July 22: RA 015 (1:02), Dec +52
July 27: RA 025 (1:39), Dec +53 Cas-Per Border
July 31: RA 030 (2:01), Dec +54 Cas-Per Border


3. A Multitude of Minor Showers...

Many minor showers are allegedly active in July. Here I will discuss a
few. Space limitations don’t give me the chance to cover them all here,
but I’ll bring up the ones that have been reported to the NAMN, that
used to be on the IMO’s Working List, and some that may have a chance
for some visual activity in the average year.

The first is the alpha Cygnids (ACG/ACY). I’m not sure what to make of
this shower. It has been the largest minor shower source reported to the
NAMN in the last 4 years, with 60 meteors. However, it’s hard to explain
how this shower, as listed, could possibly exist. The ACG shower used to
be on the IMO Working List, with RA of 315 (23:00) and Declination of
+48, very near Deneb at the tail of Cygnus. Now come some of the
problems. The activity period is shown from July 1st through September
30th from this same radiant!

As far as I know, it is physically impossible for a radiant to show no
motion in the sky during 1/4 of the earth’s annual orbit. You would
expect a shift in RA close to 90 degrees during that time. It is not in
Gary Kronk’s Meteor Shower list, and does not show up on the expansive
IAU list either. From what I have been able to determine, the original
source is from British Astronomical Association data prior to 1995.
Still, without an explanation for the impossibly fixed radiant for 3
months, I am very skeptical. Hopefully, I can obtain some original data
from the BAA that shows this “1 or 2 an hour” rate for the late summer
and early autumn. The peak is supposed to be July 15th.

So, for this year, I suggest that anyone reporting these meteors make an
extra effort to determine how close the projected path of any ACGs comes
to Deneb. If you can translate that information into RA and Dec, even
better; if you need help, feel free to contact me. A plot or photo of
the meteor would help determine the validity of the shower. Since the
radiant supposedly doesn’t move, I won’t list dates and radiant. Just
use the radiant listed above. I can find no speed listed for these
meteors either, which makes me suspect that these are sporadic meteors
assigned to a shower that might not exist. Since that’s the case any
angular velocity estimates that can be supplied would be very useful.
Perhaps we can help determine whether it’s real or not!

Nearby (but not the ACG’s) is the omicron Cygnids (OCY), as long as our
eyes are looking that way. This shower was never on the IMO list, but
does show up on the IAU database as shower #182. The reported ZHR is
2.5, so might be visible. Meteor speed is 37 km/sec, medium fast. The
peak is July 19th, practically on the full moon night, so it isn’t a
good year. The short activity period is from the 17th to 22nd. Radiant
location is 304 (20:16) +48, only about 10 degrees from Deneb, trailing
behind the tail of Cygnus.

Next up is the July Pegasids (JPE). This shower was on the old IMO
Working List, and is IAU shower #175. The listed ZHR is about 3 per
hour, though the IMO reports that activity has been low to non-existent
for the last 2 decades at least, thus it has been dropped from the
current working list. These are exceptionally fast meteors (70 km/sec)
similar to Leonids. The NAMN has recorded about 4 per year recently. The
activity period is from July 6th to 14th, so will all be before the full
moon this year. The peak night’s radiant (July 9) is RA 340 (22:39), Dec
+15. It’s not far from that position on the other nights. This is on the
edge of the Great Square of Pegasus, closest to the Circlet of Pisces.

There are also 2 showers in Phoenix, but aren’t really targets for north
American observations, and again, due to space limitations, I won’t go
into detail. Contact me if you desire more information on the PHE and
NPH showers.


4. Magnitude References...

The brightest object (other than the Sun and Moon) for most of the month
is Jupiter, glowing at magnitude -2.7 in Sagittarius. It’s bright enough
to be a distraction, but what a lovely one, especially if you use your
scope in morning twilight.

Vega, almost directly overhead is magnitude 0 (zero).

Altair in Aquila and Antares, the heart of Scorpio, are both just a
touch brighter than 1st mag, while Formalhaut, near the PAU radiant is
mag +1.2, just a bit dimmer.

The corners of Pegasus’ Great Square are +2.0, +2.5, +2.5, and +2.8, so
cover the range from +2 to +3.

The small diamond shape of Delphinus has stars of +3.6, +3.8, +4.3, and
+4.4 so give a good feel for a 4th magnitude meteor.

The Circlet of Pisces (5 stars) below Pegasus are +3.7, +4.1, +4.3,
+4.5, and +4.9

Equuleus, to the left of Delphinus consists of 4 stars of magnitude
+3.9, +4.5, +4.6, and +5.1.


5. 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.

For those who wish to look for other minor showers not listed here, or
want daily radiant positions for all the showers, drop me an e-mail at
my meteoreye address below, and I’ll send you my current Excel spreadsheet.

Feel free to contact us for questions and comments!!
-------------------------------------
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

==============================================
Here's to 'Clear Skies' for July...

July 2008 NAMN Notes
Written by Wayne T. Hally & edited by Mark Davis
==============================================
_______________________________________________
Mailing list meteorobs: meteorobs at meteorobs.org
To UNSUBSCRIBE, email: owner-meteorobs at meteorobs.org
http://lists.meteorobs.org/mailman/listinfo/meteorobs