Perseids 1994: Results

IMO-bulletin, USA-newsletters, Meteoric glow


IMO : 1994 Perseid Bulletin #2
USA-1 : First Newsletter - Bay Area / California - Peter Jenniskens
USA-2 : Second Newsletter - Bay Area / California - Peter Jenniskens
Cloud : Meteoric glow - call for observations



I N T E R N A T I O N A L     M E T E O R    O R G A N I Z A T I O N

1994 PERSEID BULLETIN #2
ISSUED 20UT, AUGUST 13, 1994

------------------------------------------------------------------------

SUMMARY:

Perseid ZHR's were normal from Aug 11.88 UT - Aug 12.30 UT being in the
range ~50-100. Starting at Aug 12.35 the ZHR began climbing significantly and
reached a peak near 250 in the 0.5 hour interval centred
about Aug 12.45 UT. The results from the single group at Honey Lake,
California reporting detailed quantitative data are supported by
qualitative data from more casual observers on the West coast. The ZHR 
dropped back to normal levels of ~50-100 by Aug 12.50 UT. No results 
immediately after Aug 12.50 UT are yet avaliable. The shower had returned 
to normal activity levels by Aug 12.88 based on European data from Austria 
and the U.K. Radio results support a peak near Aug 12.45 with higher rates 
from Aug 12.35-12.47.
------------------------------------------------------------------------

DETAILS:

J. Rendtel, I. Rendtel, A. Knoefel and D. Holman (Honey Lake, California)
have reported more details concerning their observation of the outburst 
near Aug 12.45 UT (solar longitude 139.58 (2000.0)). The following table 
lists the average ZHR's derived from their observations centred about 
the given UT times:

DATE (UT)       ZHR
Aug 12.21       50
Aug 12.25       60
Aug 12.29       60
Aug 12.33       70
Aug 12.38       110
Aug 12.42       180
Aug 12.45       225
Aug 12.48       150
Aug 12.50       80

The observers suggest that the rising flank of the outburst began near
Aug 12.35 UT (0830 UT) and was over by Aug 12.5 (1200 UT).
Peak time is essentially the same as derived in Bulletin #1 as Aug 12.45
(1030-1100 UT), but the peak ZHR (derived from the 15 minute interval
from 1045-1100) is 225, slightly lower than previously reported, however,
still in agreement within error margins. Shorter intervals (~5 minutes) 
between 1030-1100 UT easily lead to equivalent ZHR's near 400-500.
Fireballs observed by the group:

Time (UT) Interval    Number of fireballs
0338                    1
0338-0900               3
0900-1000               5
1000-1100               7
1100-1130               2


T. Wright (Marin County, California) qualitatively reports intense activity
from 1000-1100 UT, August 12 (Aug 12.42-Aug 12.46).

D. Chamberlin (Mt. Hood, Oregon) qualitatively reports a strong maximum
reached at 1045 UT, August 12 (Aug 12.45) with a visual rate of 3-4/minute.

G. Elmore (Santa Rosa, California) reports that a group of 3 observing
different sections of the sky began observing at 1045 UT and recorded 
a peak rate of 39/minute near 1045 UT, August 12 (Aug 12.45) 
which tapered to 5/minute for the group of 3 observers by 1100 UT (Aug 12.46). 
Compared the display to what he had seen visually during the 1966 Leonids.

J. Paulson (Mary's Peak, Oregon) qualitatively estimated a peak rate
of 3-4/minute in the interval 1045-1130 UT, August 12 (Aug 12.45-12.48).

C. Tribolet (Morgan Hill, California) reports peak rate higher than seen
last year in California with Lm=6 he estimates peak observed rate of 60/hr
for a half-hour interval in the range 0900-1100 UT, August 12 (Aug 12.38-12.46).

M. Smithwick (San Francisco, California) qualitatively estimates between
80-100 meteors between 1030-1130 UT (Aug 12.44-12.48) under urban skies.

B. Templeton (Freemont Peak State Park, California) qualitatively reports
group observations suggesting peak period of activity from 1030-1130 UT,
August 12 (Aug 12.44-Aug 12.48) with several minutes of activity where
a meteor was visible every 2-3 seconds. 

R. Hawkes (Sackville, New Brunswick, Canada) running MCP-CCD video
intensified system to Lm=+8.5 from 0115-0830 UT, August 12 (Aug 12.05-12.35)
reports no spectacular rates at low magnitudes and rates below 1993
numbers at corresponding times.

C. Steyaert (Belgium) reports that M. De Meyere (Deurle, Belgium)
recorded relative maximum radio forward scatter rates between 1000-1100 UT on
August 12 (Aug 12.44) with rates corresponding to 3.5 times similar
level of activity the previous night. Broad maximum in rates between
0800-1200 UT, August 12 (Aug 12.33-12.5).

R. Royer (Bishop, California) observed in group of 11 and qualitatively
notes that few meteors were seen before 0900 UT, August 12 (Aug 12.38).
After 0900 UT, rates began picking up. Combined four observer rate
(covering different quadrants of the sky) from 1100-1105 UT - 38 Perseids,
from 1130-1135 UT - 22 Perseids. Many fireballs were observed up to
magnitude -9.

S. Ennis (Elizabethtown, Kentucky) reports that radio observations on the
morning of August 12 at 144 Mhz were generally poor. Most intense flurries
of activity heard between 1048-1118 UT, August 12 (Aug 12.45-12.47).

D. Swann (Oklahoma) reports that activity was generally quiet August 12
before 0830 UT. After 0830 UT (Aug 12.35), some increase in rates were 
noticed until twilight ended observations.

M. Hann (Mounds, Oklahoma) recorded ZHR's ~90-100 in the interval
0830-1030 UT (Aug 12.35-12.44) with twilight strongly interfering in 
the last hour. A gradual increase in rates from 0430 UT (ZHR ~ 50) 
to 0830 UT (ZHR ~90) was noted.

P. Strosser (Sierra Nevada Mountains, California) qualitatively reports
a strong outburst observed under excellent sky conditions. Approximate
ZHR's reported from 0600-0800 UT ~40, from 0800-0900 UT ~100 and
from 0900-1100 UT ~600-700. Numerous fireballs were recorded in this time.

P. Jenniskens (California) reports a peak visual rate of 3/minute was
reached at 1110 UT (Aug 12.47).



NEWSLETTER  -  PERSEID project,  Bay Area/California,  August 12 1994


YES! What we were hoping for did actually happen: there was an outburst
of Perseids on friday morning August 12. Around 3:30 PDST rates started
to go up significantly, peaking at 04:10 PDST (11:10 UT). Preliminary
results, based on my counts only, indicate that the shower peaked at
a zenith hourly rate of about 190. 80 meteors/hr of that are from the
annual stream. Thus, the activity increased by a factor of 2.3. The 
duration was short again, very similar to the outburst in 1991 and 1992.

The maximum was accompanied by many bright meteors. A perseid with a
persistent train lasting for 20 seconds was seen at 03:31:14 PDST. One
with a train of 12 seconds at 04:11:11 PDST and one lasting for 7 seconds
at 04:13:44 PDST. A very bright non-Peseid was seen low in the north
eastern skies from Los Banos at 01:13:34 PDST. Many meteors were photographed.
It is not known yet if there are any multistation results. I am awaiting
the results of the other posts.


Peter Jenniskens
NASA/Ames Research Center
Mail Stop 239-4
Moffett Field
CA 94035-1000.

tel: 415-6043086
fax: 415-6041088
peter@max.arc.nasa.gov


NEWSLETTER  -  PERSEID project,  Bay Area/California,  August 15 1994

-------------------------------------------------------------------------

The meteors fulfilled all expectations!

YES! What we were hoping for did actually happen: there was an outburst
of Perseids on friday morning August 12. Around 3:10 PDST rates started
to go up significantly, peaking at 04:10 PDST (11:10 UT). Preliminary
results, based on my counts only, indicate that the shower peaked at
a zenith hourly rate of about 190. 80 meteors/hr of that are from the
annual stream (perhaps slightly enhanced over average activity as we are near
solar minimum). Thus, the activity increased by a factor of 2.3. The 
duration was short again, very similar to the outburst in 1991 and 1992.

I have never seen a night with so many bright meteors! It was wonderful. 
The maximum was accompanied by many bright meteors. A perseid with a
persistent train lasting for 20 seconds was seen at 03:31:14 PDST. One
with a train of 12 seconds at 04:11:11 PDST and one lasting for 7 seconds
at 04:13:44 PDST. A very bright non-Peseid was seen low in the north
eastern skies from Los Banos at 01:13:34 PDST. Many meteors were photographed.
It is not known yet if there are any multistation results. I am awaiting
the results of the other posts.

Prior to the event, members of the Fremont Peak Observatory Association and
the San Jose Astronomical Association, in collaboration with the Dutch
Meteor Society, had set up a camera network with sites at Fremont
Peak Observatory, Henry Coe State Park, Holler Observatory, and Los Banos
(Bay Area/Central Valley - California). Fremont Peak had to deal with a
large fire on August 11. It was contained by the evening. Park ranger
Rick Morales was tired, but photographed until 4:20 am, which was just
long enough to cover most of the outburst. Henry Coe had some interference
of car headlights earlier in the evening, but was fully operational during
the outburst. The cameras were operated by Michael Koop. Murphy hit my site
at Los Banos real bad. At 3:00 the rotating shutter of the low battery 
failed and couldn't be started again. But the cameras continued photographing
during the outburst and a match with other sites should give velocity 
(duration) information. The rotating shutter of the high battery worked fine.
Finally, Tom Rice at Holler worked part of the night with
cameras out of focus... Fortunately, he discovered this error just before the 
outburst started, at 3:00 am! Murphy was in our favor this time! 
In conclusion, the photography project was
very succesfull. Many meteors have been captured on film. Several of them
were real spectacular and should make wonderful images. We hope for several
multistation results too, but that awaits the developing of the negatives.

If you have photographed from a site in California 
in the Sierras, the Central Valley
south of Sacramento, the Bay Area, Santa Cruz Mountains or Monterey
Peninsula, you may have captured the same meteor as one of our cameras.
By matching the negatives we can derive the trajectory in the atmosphere
and the orbit in space. What I need is a list of exposure times, the
developed negatives, and a letter that states name address telephone as
well as the exact location from where you observed. The negatives will
be measured on a X-Y measuring machine and results will be calculated
(takes a while), after which the negatives will be returned to you and
you will receive a full report of the results.  


Peter Jenniskens
NASA/Ames Research Center
Mail Stop 239-4
Moffett Field
CA 94035-1000.

tel: 415-6043086
fax: 415-6041088
peter@max.arc.nasa.gov


***METEORIC GLOW: CALL FOR OBSERVATIONS***

Some hours before peak activity of the 1993 Perseid outburst, two
Dutch observing groups located at 500 km distance independantly
observed a glow in the constellation Perseus. The glow was centered
at R.A. 3h 45m, dec +40 degrees (2000.0), roughly in the area
between beta and epsilon Persei. Visually, it had dimensions of
about 10x3 degrees around 0:45 UT, some 2-2.5 hours before peak
activity. The glow has been visible for at least a quarter of an
hour and had a surface brightness in the range of magnitude +4.5-
5.5, about as bright as the Perseus Milky Way. It is the observers
opinion, that this actually was the advancing meteoroid cloud
shining by reflected sunlight in space. Given the characteristics,
atmospheric conditions and large distance between the two locations,
the possibility of an atmospheric phenomena can be excluded (one of
the observers, by the way, is an experienced professional
meteorologist of the Dutch Royal Meteorological Institute KNMI).
However, criticism has been that it was observed at the 'wrong'
location. 'Wrong' as the location might be theoretically, we DID see
it in Perseus last year!

WE STRONGLY URGE ALL OBSERVERS AROUND THE WORLD TO KEEP A CLOSE EYE
ON THE GIVEN AREA FOR SEVERAL HOURS AROUND AUGUST 12, 7:30h UT THIS
YEAR.

Continuous photography of the area using guided cameraž with fast
focal ratio lenses and not too large focal length on fast black and
white film is strongly recommended.
In case of positive observations, we should be very gratefull if you
are willing to report your observations on the phenomena to the
undersigned AS FAST AS POSSIBLE.
Electronic messages can be send by Internet to webmaster@dmsweb.org.

Surface mail:
Marco Langbroek
Jan Steenlaan 46
NL-2251 JH Voorschoten
The Netherlands

Casper Ter Kuile
Akker 145
NL-3732 XD De Bilt
The Netherlands



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