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        37307      15367 
2001        42800      16825 
2002        39941      16740 
2003        59244      24220 
2004        46204      17620 
2005       309573     139225 
2006       335880     149813 
2007       195688      60573 
2008       112794      32281 
2009        93823      26338 
2010       141809      37867 
2011       151101      41278 
2012       178821      39296 
2013       235937      59738 
2014       534243     131161 
2015       760331     198288 
2016       626120     161787 
2017       526789     143212 
2018       318884      89723 
2019       825918     201851 
2020       547267     138608 
2021       746438     175152 
2022       576742     165230 
2023       525808     150556 
2024       570319     163885 
2025       555215     157082 
2026       210841      41393