Perseids 1998: visual observations
Marco Langbroek, Voorschoten
Last night has been very clear and so I enjoyed a fruitfull session on the July meteors. This night featured amongst others my first Perseids of this year. Also, this night was dedicated to the omicron (alpha) Cygnids. Below my observational data, and an impression.
This was the first clear moonless night since June 21. A continuous series of low pressure disturbances passing over last weeks temporarily has given way to a ridge of high pressure and warmer air. A strong breeze developed yesterday, and by nighttime this resulted in a very clear sky. In the early part of my observations I counted Lm 6.4-6.5 in Aquila and Draco, which is rare for my homebound location! Occasionally a small patchy remnant of dissolving cumuli passed over at high speed, but they were no serious problem. Near the end of the night, a combination of advancing twilight, some haze developing and fatique arrising made for a drop in Lm to 6.3-6.0 and a corresponding drop in meteor numbers. Venus rose brilliantly in the southeast. There were no frogs this time, but the bats were visible and audible. A very fine night!
Meteor activity was high. Some nice examples among them, but no real bright meteors. The brightest was a +1 omicron (alpha) Cygnid in northern Ophiuchus at 00:13 UT. The omicron (alpha) Cygnids were well recognizable. Olech et al. of the Polish Comet and Meteor Workshop recently got an enjoyable paper on this stream accepted by Astronomy & Astrophysiscs. My first encounter with this stream was in 1990, observing from Puimichel (S France), and it really is a nice stream with nice meteors. I did not know of its existence at that time in 1990, so they came as a surprise (I believe I made an report on my observation published in WGN of 1991 or 1992). My data from 1990 are part of Peter Jenniskens 1994 A&A curve for the stream.
This night as mentioned also saw my first Perseids of this year (3 members). The first was a nice +2 with 0.5 s persistent train moving from Draco to southern Hercules at 23:22 UT. A second one, a +3 with a short 0.25 s train appeared at 23:34 moving from Vulpecula to Ophuichus. At 00:01 UT a +4 appeared in the same area.
A tentative calculation with my data results in an observed ZHR of 2.2 +- 1.0 for the omicron (alpha) Cygnids and 1.8 +- 1.1 for the Perseids, which is in accordance with what you would expect for this date.
Dutch Meteor Society, the Netherlands
Obs: Marco Langbroek LANMA Loc: Voorschoten, The Netherlands, 52d 07' N, 4d 28' E Date: July 18/19, 1998 UT Teff Lm oCyg aCap dAqr-N dAqr-S Per Paus Spo 22:43-00:00 1.12 6.5 2 0 0 0 2 0 13 00:00-01:05 1.03 6.1 3 1 0 1 1 0 3 TOTAL 2.15 <6.3> 5 1 0 1 3 0 16 26 stream +1 +2 +3 +4 +5 +6 Sporadics 0 3 3 5 4 1 <3.8> o Cygnids 1 0 2 2 0 0 <3.0> Perseids 0 1 1 1 0 0 <3.0> Capricornids 0 0 1 0 0 0 d Aquarids-S 0 0 1 0 0 0
Last night was weird. It started off very badly, but it ended all very well. Below my data and an impression.
After the thunderstorms of monday, the passage of a cold front resulted in clear blue skies and a strong breeze in the afternoon and evening of yesterday. Prospects seemd good. At 22:30 UT (0:30 am local) I started observations. It was a nice clear sky with Lm near +6.1, but some cumuli low in the west sounded trouble it seemed. And indeed: after 6 minutes these had entered close enough to necessitate a break of 15 minutes. Then the sky cleared again, but a new batch of cumuli was soon spotted. near 23:15 they came very near and at 23:20 I was forced to stop. At that time, it seemed it was all over for this night: the cumulus field occupied the whole sky up to the horizon, with no clearing visible. Actually this made me chagrin since daytime activities also hadn't gone too well (it is really annoying when the computer network goes down right at the moment you are trying to print the final version of a analytical report you have been working on 12 hours/day for the last 3 weeks and want to finish defenitely this week) and therefore I had looked forward to some relief through observing. Anyway, I went to sleep disappointed after only 0.57 hours observing and 6 sporadics.
About 20 mintes later, I decided to look out of my bedroom window. I guess this was some kind of 'hunch'. Guess what: yes, it was brilliantly clear from horizon to horizon! And when I say 'Brilliant', I mean 'Brilliant'! Lm 6.4 in Aquila and Draco: wow! So I quickly got dressed again and got outdoors again. From 23:50 untill 01:15 UT, I was able to harvest meteors by the number under perfect conditions: a beatifull sky (for the standards of my village) with a nice milky way. Many meteors, albeit mostly faint specimens. When twilight set in, fomalhaut was visible low in the south, with Jupiter higher up in the sky. So this night ended, quite unexpected after the bad start, very well indeed! No really eye-catching events though (brightest +1, sporadic). Some omicron Cygnids, only one early Perseid, low Capricornid and Aquarid activity. Very enjoyable!
Obs: Marco Langbroek LANMA Date: July 21/22, 1998 Loc: Voorschoten, the Netherlands, 52d 07' N, 4d 28' E UT Teff Lm dAqr Cap oCyg Per Paust Spo 22:30-23:20 0.57 6.1 0 0 0 0 0 6 23:50-01:15 1.31 6.4 2 1 3 1 0 12 TOTAL 1.88 <6.3> 2 1 3 1 0 18 25 stream +1 +2 +3 +4 +5 Sporadics 1 3 5 6 3 o Cygnids 0 1 2 0 0 d Aquarids 0 0 1 1 0 Perseids 0 0 0 1 0 Capricornids 0 0 0 1 0
|This page was last modified on July 24, 1998 by
Casper ter Kuile and Marco Langbroek