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        42796      16823 
2002        39938      16739 
2003        59225      24212 
2004        46204      17620 
2005       309544     139215 
2006       335867     149808 
2007       195665      60567 
2008       112725      32262 
2009        93765      26322 
2010       141791      37862 
2011       151054      41266 
2012       178781      39284 
2013       235868      59719 
2014       534325     131199 
2015       761009     198463 
2016       626211     161815 
2017       526905     143246 
2018       318797      89699 
2019       825771     201815 
2020       547175     138593 
2021       746239     175095 
2022       576516     165166 
2023       525673     150518 
2024       570200     163852 
2025       554924     157038 
2026       212671      41901