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         2795        955 
1998        24453      10290 
1999        13274       5066 
2000        37298      15363 
2001        42780      16817 
2002        39914      16735 
2003        59200      24202 
2004        46189      17614 
2005       309420     139170 
2006       335787     149775 
2007       195620      60555 
2008       112608      32230 
2009        93548      26263 
2010       141720      37842 
2011       150935      41234 
2012       178620      39241 
2013       235583      59638 
2014       533354     130978 
2015       760517     198382 
2016       626891     162003 
2017       526919     143283 
2018       318519      89622 
2019       825560     201764 
2020       546557     138452 
2021       745570     174901 
2022       575808     164962 
2023       525278     150404 
2024       569934     163755 
2025       554261     156886 
2026       219800      44306