The Quadrantids are always the first active meteor shower of the year. The Quadrantids show a sharp maximum around January 4, which unfortunately only lasts a short time. As a result, the numbers of Quadrantids that are visible each year are very variable. If the maximum falls during the day, you will see much less in the nights before and after it than when the maximum falls in the second part of the night. And that can make a big difference in the numbers of observed meteors.
Furthermore, the Quadrantids also show varying maximum activity due to planetary disturbances. The Quadrantids usually peak with a ZHR of 80, but there have also been years when the ZHR was much higher. During the ice-cold and crystal-clear night 3/4 January 1995, the ZHR reached around 140 with the ZHR above 100 until dawn [1, 2, 3]. The legendary DMS visual and photographic campaign from 1995 also produced a clue for the parent body of the Quadrantids [4] 2003 EH1 .
Also in 2009, a ZHR of 140 was observed, this time above America [6] and the period before that above Europe it was obvious that the Quadrantids were more active than what you normally would expect [5].
The astronomical circumstances for the Quadrantids in 2019 were particularly good for Europe with a predicted maximum on January 4 around 02:00 UT.
Unfortunately, the weather in January rarely cooperates. So, from the BeNeLux it was only possible to observe for a few hours in the evening when the radiant was still low in the north-west and north. Sky got cloudy after 23:00 UT due to an incoming front.
According to the live ZHR graph on the IMO website the Quadrantids in 2019 had a maximum ZHR of 116 on 4 January 2019 at 02:20 UT. After that the Quadrantids showed declining activity with a ZHR of 80 at 06:00 UT. A total of 35 observers reported 1993 Quadrantids to IMO. Enough for a comprehensive analysis!

Collecting the visual data
The data was collected via the IMO site and immediately checked for limiting magnitude (at least 5.9) and whether a good CP determination was available from the relevant observer. After entering all data, 1761 Quadrantids were used for the analysis. Once in the spreadsheet all data with lower radiant positions than rounded off 25 degrees were deleted. Fortunately, just a few meteors fell off. A total of 1749 Quadrantides remained available for the final analysis.
For both the population index r and ZHR, the data is checked on different criteria. That is also the reason why fewer meteors were used for the population index r than in the final ZHR calculations.

Population index r
To be able to make a good ZHR determination, the population index r must first be calculated. For this, the magnitude distributions of all observers were checked. The rule here is that the difference between the limiting magnitude and the average magnitude of the observed meteors may not be bigger than 4.0 magnitude. After checking the data, 1283 Quadrantids were used to determine the population index r. The results of these calculations are shown in Tables 1 and 2 and Figure 1.
The result is what you would expect for the Quadrantids, only the fairly high population index r on 4 January 04:30 UT does not fit completely in the picture. It is clear that the population index r is the lowest over America, something you would expect with the Quadrantids in 2019. The bright Quadrantids appear mainly after the maximum.
For the ZHR calculations a fixed r value was used for this night, determined on the basis of r [-2; 5] and all Quadrantids observed between 3 January 2019 23 UT and 4 January 2019 12 UT. In total, a population index r 2.73 ± 0.05 [7] was calculated from 1283 Quadrantides. Too few Quadrantids were observed during the night of 2/3 January to calculate a good population index r. The average magnitude that night was a bit lower than 3/4 January. For that reason, the population index r for that night was kept at r = 3.00.

Table 1: Results of population index r calculations.

Figure 1. Population index r gradient over the night 3/4 January 2019.


Table 2. Population index 3 for the period between
January 3, 2019 23:00 UT and January 4, 2019 12:00 UT.

The final ZHR calculation were made with population index r = 2.73 for the night 3/4 January and for the night 2/3 January an assumed population index r = 3.00 was used. A total of 1530 Quadrantids were used to calculate the ZHR. For the calculations 15 – 20-minute counts were used. Some observers sent in shorter counting periods, these were merged. The results of the calculations can be seen in Table 3 and Figure 2.

Table 3. ZHR Quadrantids 2019.

Clearly a peak of the ZHR is visible at solar longitude 283.15, which is on 4 January 2019 at 02:05 UT. This time is very close to the time of the on-the-fly curve on the IMO site. With a ZHR of 120 this is a good return of the Quadrantids and comparable with the returns from 1995 and 2009.
In Figure 3 the curve from 1995 has been added (own analysis 2009). Despite the fact that the 1995 Quadrantid curve was determined on the basis of 1 hour counts and that of 2019 on the basis of 20
minutes there is some agreement. The peak in 1995 is a bit later in solar longitude.

Figure 3. Quadrantids ZHR profiles from 1995 and 2019

2019 was a good Quadrantid year, with a maximum ZHR of around 120. The time of the maximum was almost at the predicted time of January 4, 2019 around 02:00 UT. It is recommended for the Quadrantids during their maximum to observe in counting periods of 5 minutes.

A big thank you to all observers who observed the 2019 Quadrantids. These observers are: Orlando Benitez Sanchez, Larry Black, Martin Davies, Michel Deconinck, Sietse Dijkstra, Kai Gaarder, Gerardo Jiménez López, Károly Jónás, Javor Kac,Omri Katz, André Knöfel, Selma Koelers, Anna Levin, Ole Lit, Pierre Martin, Fabrizio Melandri, Shai Mizrachi, Arash Nabizadeh Haghighi, Francisco Ocaña González, Jonas Plum, Pedro Pérez Corujo, Ella Ratz, Jurgen Rendtel, Branislav Savic, Kai Schultze, Costantino Sigismondi, Ulrich Sperberg, Hanjie Tan, István Tepliczky, Shigeo Uchiyama, Peter van Leuteren, Hendrik Vandenbruaene, Michel Vandeputte, Valentin Velkov , Thomas Weiland, Ariel Westfried, Patrick Wullaert en Sabine Wächter.
Also, a word of thanks to Carl Johannink, Paul Roggemans and Michel Vandeputte for the useful comments on this article.

[1] Ter Kuile, C., Historische Boötidenactie te Biddinghuizen!, Radiant 17-1, p. 21-28.
[2] Van Vliet M., Bootiden 1995: Visuele waarnemingen.
[3] Langbroek M, Een zeldzaam mooi Boötidenmaximum, Zenit april 1995, p. 178-179.
[4] Jenniskens P., Quadrantids 2003 EH1 and the Quadrantid Shower, WGN 32/1 (2004) p.7-10.
[5] Vandeputte M., Quadrantiden vanuit Ermelo, eRadiant 2009-1, p. 10-13.
[6] Johannink C., Miskotte K., De Quadrantiden in 2009: een leuke verrassing!, eRadiant 2009-2, p. 43-50.