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        42780      16817 
2002        39935      16738 
2003        59204      24204 
2004        46196      17617 
2005       309476     139190 
2006       335817     149788 
2007       195646      60562 
2008       112645      32240 
2009        93630      26285 
2010       141737      37847 
2011       150989      41249 
2012       178657      39251 
2013       235684      59667 
2014       533332     130968 
2015       760427     198355 
2016       626591     161923 
2017       526561     143192 
2018       318621      89650 
2019       825533     201751 
2020       546781     138514 
2021       745782     174963 
2022       576061     165035 
2023       525429     150449 
2024       569924     163774 
2025       554483     156932 
2026       218002      43618