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          465        177 
1992          730        296 
1993         1283        478 
1994         1643        604 
1995         2927       1023 
1996         2927       1035 
1997         1801        624 
1998        21512       9153 
1999        12981       4999 
2000        38143      15761 
2001        39058      15163 
2002        31632      14044 
2003        56906      23702 
2004        45689      17549 
2005        80330      24750 
2006       103526      33276 
2007       189208      58592 
2008       108760      31211 
2009        90803      25622 
2010       142585      38338 
2011       153071      42493 
2012       144487      40070 
2013       216715      61796 
2014       554506     141242 
2015       794377     208936 
2016       651107     169113 
2017       547339     148140 
2018       342899      96386 
2019       854751     208529 
2020       601912     152947 
2021       812018     192431 
2022       611691     175116 
2023       551808     157909 
2024       606073     174468 
2025       436549     124366