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         1666        612 
1995         3006       1050 
1996         2959       1046 
1997         1828        633 
1998        21610       9194 
1999        13253       5094 
2000        38513      15923 
2001        39311      15271 
2002        33171      14587 
2003        57598      23974 
2004        46202      17734 
2005        81083      24975 
2006       104628      33603 
2007       191313      59160 
2008       111825      32032 
2009        92588      26109 
2010       144992      38954 
2011       157086      43592 
2012       148430      41140 
2013       220196      62754 
2014       564891     143943 
2015       798221     210139 
2016       657880     170975 
2017       554276     150039 
2018       350775      98555 
2019       862856     210643 
2020       616169     156822 
2021       829010     196840 
2022       619084     177218 
2023       558215     159691 
2024       616982     177798 
2025       219942      62860