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          705        287 
1993         1261        470 
1994         1599        589 
1995         2797        980 
1996         2814        997 
1997         2789        953 
1998        24436      10284 
1999        13249       5058 
2000        37284      15357 
2001        42766      16810 
2002        39884      16723 
2003        59170      24189 
2004        46136      17595 
2005       309274     139121 
2006       335701     149742 
2007       195526      60530 
2008       112389      32169 
2009        93309      26195 
2010       141521      37789 
2011       150706      41171 
2012       178322      39162 
2013       235182      59526 
2014       533485     131041 
2015       759608     198144 
2016       626666     161953 
2017       526644     143196 
2018       315453      89053 
2019       824205     201687 
2020       547170     138648 
2021       744165     174551 
2022       574739     164662 
2023       524463     150174 
2024       569116     163532 
2025       551308     156176 
2026       228841      47071