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        58486      23942 
2004        46017      17546 
2005       308738     138915 
2006       335322     149597 
2007       195075      60408 
2008       111915      32042 
2009        92755      26045 
2010       140951      37641 
2011       149767      40914 
2012       177385      38909 
2013       233985      59191 
2014       531335     130479 
2015       756357     197273 
2016       626530     161924 
2017       525324     142867 
2018       313597      88544 
2019       821923     201148 
2020       543244     137621 
2021       737601     172874 
2022       571617     163776 
2023       522239     149550 
2024       566181     162689 
2025       548348     155026 
2026       236420      49435