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        37305      15366 
2001        42800      16825 
2002        39938      16739 
2003        59230      24214 
2004        46204      17620 
2005       309553     139219 
2006       335874     149811 
2007       195673      60569 
2008       112755      32270 
2009        93786      26328 
2010       141797      37864 
2011       151080      41273 
2012       178806      39291 
2013       235894      59726 
2014       534393     131214 
2015       760907     198434 
2016       626195     161810 
2017       526859     143233 
2018       318824      89706 
2019       825879     201841 
2020       547198     138592 
2021       746326     175119 
2022       576590     165187 
2023       525720     150531 
2024       570250     163866 
2025       555175     157070 
2026       212711      41911