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
