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          228         81 
1991          867        310 
1992          716        291 
1993         1264        471 
1994         1616        595 
1995         2825        989 
1996         2832       1003 
1997         2828        966 
1998        24510      10310 
1999        13346       5093 
2000        37513      15461 
2001        43039      16927 
2002        40213      16860 
2003        59377      24289 
2004        46474      17731 
2005       310629     139634 
2006       336954     150217 
2007       196583      60802 
2008       114132      32640 
2009        95332      26746 
2010       145320      38735 
2011       153110      41827 
2012       181354      39980 
2013       238976      60580 
2014       534511     131138 
2015       765159     199579 
2016       618576     159665 
2017       531540     144458 
2018       323557      91054 
2019       829905     202775 
2020       556298     140909 
2021       760182     178800 
2022       583299     167096 
2023       531524     152178 
2024       577431     165928 
2025       569491     162814 
2026        91138      24259