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          468        178 
1992          740        300 
1993         1296        483 
1994         1658        609 
1995         2991       1045 
1996         2953       1044 
1997         1822        631 
1998        21587       9186 
1999        13138       5054 
2000        38411      15877 
2001        39246      15243 
2002        31673      14079 
2003        57454      23916 
2004        46085      17691 
2005        80836      24902 
2006       104276      33499 
2007       190810      59024 
2008       111120      31844 
2009        92150      25989 
2010       144287      38778 
2011       156038      43308 
2012       147483      40884 
2013       219047      62441 
2014       562689     143413 
2015       799019     210206 
2016       656111     170492 
2017       551938     149440 
2018       349135      98106 
2019       860793     210135 
2020       613420     156100 
2021       824758     195777 
2022       616931     176600 
2023       556008     159063 
2024       612680     176499 
2025       287167      82642