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        24682      10373 
1999        13483       5143 
2000        37900      15637 
2001        43393      17085 
2002        40643      17046 
2003        60512      24726 
2004        47186      17999 
2005       312901     140513 
2006       339223     151096 
2007       198824      61419 
2008       116966      33410 
2009        97870      27422 
2010       148248      39455 
2011       157962      43138 
2012       186188      41302 
2013       244802      62188 
2014       563097     137996 
2015       812898     210331 
2016       634291     163602 
2017       545969     147873 
2018       333487      93744 
2019       845369     206576 
2020       583123     147727 
2021       793838     187595 
2022       601796     172286 
2023       543211     155440 
2024       599716     172313 
2025       585337     167319