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          746        302 
1993         1308        487 
1994         1684        618 
1995         3099       1081 
1996         2986       1055 
1997         1890        652 
1998        22325       9434 
1999        13590       5215 
2000        38768      16033 
2001        39562      15371 
2002        32105      14252 
2003        58050      24149 
2004        46599      17879 
2005        81915      25211 
2006       105568      33872 
2007       192866      59573 
2008       114351      32698 
2009        94332      26578 
2010       115972      32108 
2011       160443      44485 
2012       151714      42034 
2013       224323      63896 
2014       568598     144864 
2015       799998     209517 
2016       666164     172810 
2017       558541     151038 
2018       356145     100030 
2019       872119     212920 
2020       624860     159086 
2021       843419     200572 
2022       628903     180007 
2023       564845     161547 
2024       631439     181794 
2025       169386      48247