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        13259       5062 
2000        37288      15359 
2001        42774      16814 
2002        39893      16726 
2003        59178      24193 
2004        46157      17603 
2005       309326     139137 
2006       335736     149756 
2007       195579      60544 
2008       112451      32186 
2009        93350      26207 
2010       141621      37815 
2011       150813      41200 
2012       178429      39191 
2013       235275      59551 
2014       533744     131110 
2015       759905     198227 
2016       626896     162008 
2017       526834     143245 
2018       315717      89129 
2019       824493     201770 
2020       546553     138458 
2021       744870     174710 
2022       575037     164745 
2023       524670     150232 
2024       569426     163617 
2025       551699     156632 
2026       224994      45804