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          708        288 
1993         1261        470 
1994         1599        589 
1995         2797        980 
1996         2814        997 
1997         2789        953 
1998        24439      10285 
1999        13262       5063 
2000        37290      15360 
2001        42774      16814 
2002        39893      16726 
2003        59180      24194 
2004        46166      17606 
2005       309333     139139 
2006       335736     149756 
2007       195583      60545 
2008       112463      32189 
2009        93366      26212 
2010       141647      37823 
2011       150820      41202 
2012       178447      39196 
2013       235302      59558 
2014       533767     131116 
2015       759933     198233 
2016       626857     162000 
2017       526862     143255 
2018       315744      89137 
2019       824163     201661 
2020       546237     138368 
2021       744933     174726 
2022       575071     164755 
2023       524713     150244 
2024       569576     163660 
2025       553755     156750 
2026       225075      45826