Eta Aquariids: enhanced activity in 2013
In the period of early may the meteorshower the eta Aquariids (ETA) are active. It is one of the most active meteor showers visible in the southern Hemisphere. From the Netherlands the shower is poorly visible, because the moment the radiant rises above the horizon, the twilight set's in. After that there is a 90 minute window to observe one or two ETA's and if you are really lucky sometimes you could count three ETA's. The data collected from the Netherlands is not suitable for serious ZHR analysis . The radiant still is on 12 degrees elevation when dusk is to bright to observe meteors. ZHR calculations are only done with radiantheights above 30 degrees. This year I could observe during two nights, the other nights were (partly) clouded or to hazy.
4/5 May 2013
It was weekend so I could observe a little longer. After starting up the all sky camera and CAMS Watec camera in the twilight I took a short nap. I started the observation at 23:30 UT under a very clear sky. Somewhat earlier that night clouds passed by and the last remnants were visible low in the southeast. Limiting magnitude was 6.5. The Milky Way was visible from Cassiopeia to Scutum. Scorpius is visible low in the south, stars of the constellation Sagitarius more to the east, while Spica and Saturn were already in the southwest. It was extreme calm that night (no traffic, no drunks going home and some ground fog in the last hour it, so was fun to enjoy the starry sky. When I stopped because of the twiligt all birds were active with the most prominent one a Cuckoo.
I could observe between 23:30 and 02:31 UT. The first two periods yielded nice meteor activity, in particular the number eta Lyrids (ELY) strucked me. Between 23:30 and 01:00 UT I counted 13 meteors including 2 ELY and 1 ANT. The most beautiful meteor in this period was at 23:33 UT when one fine +2 ELY appeared in Hercules.
At 01:00 UT I changed my field of view from southeast to east so I had the ETA radiant in my sight. The proportion of sporadic meteors and eta Lyrids were significantly higher in this period. I counted 3 ELY and 2 ANT seen. Also some bright meteors were seen:
01:10 UT: a nice +2 ANT made a long track through Aquila, Delphinus and Pegasus
01:11 UT: white +1 SPO appears in Pegasus
01:24 UT: the first and only ETA is seen, magnitude +4
02:07 UT: beautiful +1 ELY in Cassiopeia
02:17 UT: the highlight of the night appears in deep twilight, a rapid sporadic meteor with two flares of magnitude -1 or -2 in Hercules.
In total I observed this night effective 3.00 hours and counted 29 meteors, including 1 ETA, 3 ANT and 5 ELY.
May 5/6 2013
The next night I was back on the heath at 23:28 UT. The sky was slightly less in quality than the previous night, a difference that was particularly noticeable at low altitude. Roughly limiting magnitude was a tenth less than yesterday. The first period ran from 23:28 to 01:00. Oh oh, what a boring show! Only 9 meteors seen in this period (yesterday i counted 13 in the almost the same period). One ELY and 1 ANT were seen,and the brightest meteor was a +2 SPO.
After 01:00 UT I payd again attention to the ETA's. Radiant above the horizon at 01:10 UT and just before 01:30 UT I saw one: a +3 ETA shot throught Cepheus. Meanwhile some ground fog started to appear, but it did not affected the sky quality.
01:37:55 UT: Wonderful! One of the most beautiful ETA's I have ever seen! A magnitude +1, bluish, draws a gorgeous long trail through Aquila, Ophiuchus and Virgo (extinguishing halfway Spica /Saturn). A trail of 110 degrees! Wow, this was one of the finest ETA earth grazers that I have ever seen!
01:47 UT: another beautiful blue yellow ETA draws a long track throught Delphinus and Aquila, the last part perhaps in the CAMS field. A long track despite the proximity of the ETA radiant and again is a short-lasting persistent train visible. Hey, that's quite fast, three ETA's within 20 minutes. I also remember at that time the email of Mikya Sato, he expected elevated ETA counts because some old dusttrails of comet 1P Halley were near the earth. The tension is rising rapidly. Meanwhile, the surrounding ground fog became thicker which resulted in a but hazy sky below 5 degrees altitude.
01:55 UT: bang, again a bright ETA. A +1 ETA appears low in the north with a lasting train. Now it is clear to me that there is something special going on. And soon more ETA started to appear.
02:01 UT: +4 ETA in Cygnus pulling a long track.
02:03 UT: a very nice +2 ETA in Aquila with a short persistent train.
02:06 UT: Superb! +1 ETA with a short persistence train shot through Delphinus, Aquila and Ophiuchus. This ETA is actually recorded with the CAMS camera.
02:17 UT: +3 ETA in Cygnus with a lasting train. I decide not to stop at 02:30 UT, but to continue until the sky became to bright.
02:32 UT: Pats! A bright yellow -2 ETA very low east at 5 degrees elevation in the middle of the bright twilight! Despite the high DCV of 40 degrees it was spotted easily. Maybe this one was much brighter (no comparison objects at that height) ....
02:43 UT: I shortly look at the west, bang! From the zenith a magnitude 0 shot through Bootes. If I check a few seconds later it was an ETA (and that was it ...):
02:43 UT: bang! Another bright ETA A -1 or -2 ETA (or brighter) at dusk in Pegasus.
02:56 UT: +1 or 0 ETA south, no comparison stars ...
At 03:02 UT I stopped the observations, the sky is way to bright. But boy, what a cool show I did see. At home I shut down the CAMS and the all sky camera and sent a message to Meteoren NV and a response on Michel's findings on Meteorobs. Later that day it turned out that “my” CAMS captured 6 ETA that morning, of which 3 were simultaneously with the CAMS station at Gronau (Carl Johannink).
Leonid observations of Koen Miskotte