Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          471        179 
1992          743        301 
1993         1308        487 
1994         1681        617 
1995         3051       1065 
1996         2980       1053 
1997         1863        643 
1998        21682       9218 
1999        13530       5190 
2000        38624      15968 
2001        39452      15324 
2002        32602      14405 
2003        57762      24033 
2004        46340      17779 
2005        81433      25067 
2006       105094      33730 
2007       191891      59309 
2008       112429      32191 
2009        93210      26271 
2010       141256      38131 
2011       158182      43875 
2012       149453      41408 
2013       221338      63056 
2014       564587     143847 
2015       798542     210158 
2016       659414     171364 
2017       554969     150216 
2018       351889      98855 
2019       864057     210906 
2020       617511     157156 
2021       831032     197344 
2022       620407     177577 
2023       558788     159827 
2024       617582     177928 
2025       212381      60720