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          219         78 
1991          864        309 
1992          675        277 
1993         1222        457 
1994         1593        587 
1995         2708        950 
1996         2802        993 
1997         2774        948 
1998        24408      10272 
1999        13181       5034 
2000        37221      15327 
2001        42258      16629 
2002        35799      15341 
2003        58495      23945 
2004        46023      17548 
2005       308748     138918 
2006       335329     149600 
2007       195086      60411 
2008       111919      32043 
2009        92766      26048 
2010       140963      37644 
2011       149784      40919 
2012       177415      38917 
2013       234034      59205 
2014       531392     130494 
2015       756365     197273 
2016       626133     161813 
2017       525284     142855 
2018       313676      88566 
2019       821964     201158 
2020       543313     137640 
2021       737682     172897 
2022       571654     163787 
2023       522279     149561 
2024       566195     162693 
2025       548387     155035 
2026       235816      49263