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          743        301 
1993         1308        487 
1994         1678        616 
1995         3051       1065 
1996         2980       1053 
1997         1860        642 
1998        21679       9217 
1999        13519       5186 
2000        38624      15968 
2001        39447      15322 
2002        32602      14405 
2003        57756      24030 
2004        46338      17778 
2005        81423      25064 
2006       105090      33729 
2007       191872      59304 
2008       112410      32186 
2009        93176      26262 
2010       141245      38128 
2011       158109      43856 
2012       149422      41399 
2013       221256      63033 
2014       564760     143888 
2015       798570     210169 
2016       659329     171343 
2017       554919     150201 
2018       351797      98827 
2019       864027     210899 
2020       617454     157142 
2021       830819     197292 
2022       620244     177529 
2023       558722     159809 
2024       617825     177998 
2025       212437      60736