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          713        290 
1993         1261        470 
1994         1604        591 
1995         2804        982 
1996         2814        997 
1997         2798        956 
1998        24464      10294 
1999        13290       5072 
2000        37303      15365 
2001        42791      16821 
2002        39938      16739 
2003        59218      24209 
2004        46201      17619 
2005       309530     139210 
2006       335855     149803 
2007       195665      60567 
2008       112702      32256 
2009        93746      26317 
2010       141781      37859 
2011       151044      41263 
2012       178754      39277 
2013       235813      59703 
2014       534294     131191 
2015       761085     198484 
2016       626316     161841 
2017       526646     143208 
2018       318755      89688 
2019       825688     201792 
2020       547118     138580 
2021       746157     175072 
2022       576399     165133 
2023       525597     150495 
2024       570177     163845 
2025       554895     157029 
2026       213414      42132