Year Observations     Objects
1858            3          3 
1889            1          1 
1901            1          1 
1920            6          2 
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           14          7 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          231         82 
1991          867        310 
1992          721        293 
1993         1280        477 
1994         1628        599 
1995         2881       1008 
1996         2886       1021 
1997         2927        999 
1998        24676      10371 
1999        13483       5143 
2000        37898      15636 
2001        43383      17081 
2002        40622      17037 
2003        60494      24718 
2004        47152      17987 
2005       312752     140455 
2006       339032     151024 
2007       198655      61373 
2008       116622      33317 
2009        97664      27372 
2010       147911      39393 
2011       157533      43019 
2012       185756      41184 
2013       244307      62055 
2014       562117     137731 
2015       812103     210117 
2016       632772     163145 
2017       545413     147735 
2018       332746      93532 
2019       844501     206340 
2020       580737     147135 
2021       791657     186961 
2022       600674     171966 
2023       542321     155189 
2024       598034     171842 
2025       584865     166907