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         2771        947 
1998        24408      10272 
1999        13181       5034 
2000        37221      15327 
2001        42256      16628 
2002        35796      15340 
2003        58486      23942 
2004        46017      17546 
2005       308738     138915 
2006       335320     149596 
2007       195075      60408 
2008       111909      32040 
2009        92755      26045 
2010       140936      37637 
2011       149755      40911 
2012       177377      38907 
2013       233979      59189 
2014       531318     130474 
2015       756360     197273 
2016       626584     161942 
2017       525310     142863 
2018       313584      88540 
2019       821921     201148 
2020       543235     137618 
2021       737576     172867 
2022       571602     163772 
2023       522236     149549 
2024       566178     162688 
2025       548340     155024 
2026       236733      49527