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         1661        610 
1995         2994       1046 
1996         2953       1044 
1997         1822        631 
1998        21587       9186 
1999        13144       5056 
2000        38415      15879 
2001        39248      15244 
2002        32668      14411 
2003        57454      23916 
2004        46091      17693 
2005        80836      24902 
2006       104290      33503 
2007       190828      59029 
2008       111138      31849 
2009        92154      25990 
2010       144303      38782 
2011       156053      43312 
2012       147491      40886 
2013       219070      62447 
2014       562755     143429 
2015       798821     210171 
2016       656096     170491 
2017       551969     149449 
2018       349143      98109 
2019       860778     210133 
2020       613410     156095 
2021       824826     195794 
2022       616969     176611 
2023       556028     159069 
2024       612755     176519 
2025       287281      82673