1 Introduction
Every year the first week of May is a special period for meteor observers in Belgium and the Netherlands. Early May the meteor shower the η-Aquariids (ETA) reaches its maximum. From the Benelux, the meteor shower is difficult to observe. As the ETA radiant rises above the horizon around 3:15 local time, at the same time begins the astronomical twilight. To 4:00 pm local time, you can observe well, after that, dusk is getting on quickly. Some observers continue until 5:00 pm local time, as only stars of +2 or brighter are visible. ETA observations from the Benelux cannot be used for normal activity profiles that we use for other meteor showers. After all, the radiant level remains far below the required 30 degrees altitude between 3:15 and 5:00 pm local time.
For visual meteor observers in the Benelux it is a sport to see an η-Aquariid before the sky gets too bright. Marco Langbroek wrote in 1995 an article about thist (Langbroek, 1995). Indeed there are one, two and very occasionally three ETA’s to be seen, but often also nothing! Exception was 2013 when the ETA’s had increased activity (Johannink, 2013). The author then counted 12 ETAs including some fine earth grazers. The period of May 3 to 7 is the most important, because the meteor shower reaches a maximum ZHR in this period of time which is variable between 40–80.
Early May 2016 we had a nice weather period in the Benelux so that I was able to observe a lot. In addition to the ETA’s there were also other sources of meteor activity: the η-Lyrids (ELY) and the Antihelions (ANT). Below are the reports.
2 The observing reports
The first clear night was April 30th / May 1st. The hunt was opened on the ETAs! A few clouds were expected, so I observed from the meteor roof of my house. Limiting magnitude around 6.3 with a nice dark sky background. I observed between 23:30 and 02:30 UT and in those three hours observing time I only saw 17 meteors of which 1 Anti Helion. No ELY and ETA’s.
The following night of May 1/2, was entirely clear. Monday is my day off so I decided to observe from the Groevenbeekse Heide, a heath near my house. I observed between 23:15 and 02:40 UT. In that period there was some problems with haze formation in the beginning of the session, but later the situation improved greatly. Also the cirrus which was constantly present low in the west stayed out of my field of view until 02:30 UT. This session from 3,40 hours yielded 27 meteors from which 1 ELY, 1 ANT and yes 1 ETA. The first one of this year. This +4 ETA appeared on 01:46 UT and put a relatively long trail down from Cepheus to Ursa Minor. During the observing session two bright meteors were observed, at 00:03 UT, a fast white sporadic (SPO) meteor was seen with a 2 second persistent train. And somewhat later a 0 SPO was seen. This night was a cold one, with temperatures that dropped to -2 degree C at ground level.
The third night which could be observed was May 3/4. A shorter session from the meteor roof because today I had to go to work. I could observe between 23:55 and 02:24 UT with a result of 17 meteors at 2,48 hours of effective observation time. Amongst them were 2 ELY 1 ETA (2nd of this year) and no ANT’s. The. ETA appeared at a time when I no longer expecting to see an ETA, a few minutes before the end of this session. Also this night temperatures got just below freezing.
The night May 4/5 was also entirely clear, because it was Ascension Day and I did not have to work. That meant I could observe from the Groevenbeekse Heide. When I started up the all sky camera and the CAMS camera’s it still did not look so very beautiful: there were quite a bit of cirrus clouds. I hoped it would get dissolving like previous night. And indeed, that happened. Only very low in western and eastern directions remained some cirrus clouds. When I started the session the lm was somewhat disappointing: 6,3 despite the fairly dark sky background. Some patches of very thin cirrus was visible, similar to the weaker parts of the galaxy. I could observe between 23:55 and 02:46 UT. During effectively 2,85 hours I observed 25 meteors. The first hour 23:55-01:00 UT was quiet with 8 meteors (including one ANT + 3). The second hour (01:00-02:00 UT) was fine with quite a few meteors and bright ones too! At 01:04 and 01:20 UT two fast +1 sporadic meteors were seen. Highlight, however, was a very beautiful magnitude 0 or -1 Anti Helion which had a long path from the northern parts of Ophiuchus, by Hercules, Draco and extinguished in Cepheus. The yellow meteor exhibited a varying brightness and showed a short wake. These are still the pearls for which I lie in the field. In addition, this hour I observed two ETA’s (+3, +5) observed at 1:35 and 1:51 UT, respectively. The last period ran from 02:00 to 02:46 UT and yielded only 3 sporadic meteors through the twilight on.
The nights 5/6 and 6/7 May in were clear but with a lot of cirrus clouds. Thus, these were not observed visually.
This bright sporadic meteor was captured on two FF files on May 5, 2016 at 23:52:53 UT.
Clearly visible is a short wake.
Bright Eta Aquariid captured on May 6, 2016 at 02:08 UT.
The night of May 7/8 was okay again, beautifully clear sky in which the lm rose to 6.4. Again I observed from the Groevenbeekse Heide and watching meteors between 23:30 and 02:40 UT. During this session I counted 26 meteors among which 5 ELY, 1 ANT and 2 ETA’s. Again some beautiful meteors were observed; at 02:52 UT a +2 ELY and at 00:25 UT a +1 ELY which both appeared in Cygnus. The best meteor was a very nice magnitude 0 ETA earth grazer. This meteor started just east of the star eta Cygnus and moved along the “head” of Draco, Lyra, Hercules, Bootes and extinguished in Canes Venatici. WOW! This is what I wanted to see. A second ETA was seen a few minutes before the end of the session. This one was also captured with my CAMS 351 camera.
This Eta Aquariid was also seen visually by the author.
The night of May, 8/9 was very clear. All day beautiful blue skies almost Provencal. And it stayed that clear at night, so I decided to start a little earlier. I could observe meteors between 22:37 and 02:32 UT. Just before 01:00 UT I took a short power nap to be fully fit for the eta Aquariids period.
Unfortunately, this night was in respect of the meteors a bit disappointing. Despite a very bright sky, I saw effective per hour less meteors. No bright meteors, the brightest were two SPO +2. In total, I saw in 3,83 hours effective 27 meteors including 4 ELY, 1 ETA (+4) and 1 ANT. Fortunately, the stunning view of the starry sky was quite a saving grace. The Milky Way was visible from Cassiopeia into the southern part of Ophiuchus and slightly right below that part the particularly attractive trio Saturn, Mars and Antares were visible in the constellation Scorpius!
In a summary, I can say that this year’s ETA hunt was very successful. For 6 nights I counted 7 ETA’s. Outside of the special year 2013 (13 ETA’s in two nights) a record! The all sky camera captured three bright meteors in this period and also both CAMS cameras were successful and captured a dozen ETA’s.
References
[1] Langbroek M., The Tale of Two Mad Meteor Hunters, WGN 23:6 (1995), page 251-253.
[2] Johannink C., Jobse K., Breukers M., Neels P.,Langbroek M, Haas R., Miskotte K., Biets J.M., Eta Aquariiden uitbarsting waargenomen met CAMS, eRadiant 2013-2, page 35-37
[3] Miskotte K., Meteoren, kometen en vuurbollen in het voorjaar van 2013, eRadiant 2013-2, page 47-55.
