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          231         82 
1991          867        310 
1992          721        293 
1993         1280        477 
1994         1628        599 
1995         2884       1009 
1996         2886       1021 
1997         2927        999 
1998        24682      10373 
1999        13491       5146 
2000        37906      15640 
2001        43399      17088 
2002        40648      17048 
2003        60516      24728 
2004        47203      18005 
2005       312925     140521 
2006       339266     151110 
2007       198902      61440 
2008       117096      33446 
2009        97923      27436 
2010       148319      39473 
2011       158102      43175 
2012       186322      41338 
2013       244912      62219 
2014       563332     138062 
2015       813164     210405 
2016       634631     163692 
2017       545900     147849 
2018       333770      93823 
2019       845674     206650 
2020       583588     147858 
2021       794228     187703 
2022       602096     172374 
2023       543388     155491 
2024       600011     172400 
2025       580635     165733