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        35799      15341 
2003        58489      23943 
2004        46023      17548 
2005       308741     138916 
2006       335322     149597 
2007       195079      60409 
2008       111919      32043 
2009        92759      26046 
2010       140963      37644 
2011       149773      40916 
2012       177404      38914 
2013       234005      59197 
2014       531367     130487 
2015       756379     197277 
2016       626292     161859 
2017       525297     142859 
2018       313629      88553 
2019       821954     201155 
2020       543296     137635 
2021       737654     172889 
2022       571629     163780 
2023       522265     149557 
2024       566195     162693 
2025       548373     155033 
2026       236049      49327