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        42256      16628 
2002        35796      15340 
2003        58489      23943 
2004        46020      17547 
2005       308738     138915 
2006       335322     149597 
2007       195079      60409 
2008       111919      32043 
2009        92755      26045 
2010       140955      37642 
2011       149767      40914 
2012       177397      38912 
2013       233991      59193 
2014       531350     130483 
2015       756372     197276 
2016       626401     161887 
2017       525297     142859 
2018       313607      88547 
2019       821936     201151 
2020       543272     137628 
2021       737641     172885 
2022       571623     163778 
2023       522246     149552 
2024       566185     162690 
2025       548363     155030 
2026       236400      49428