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          743        301 
1993         1308        487 
1994         1681        617 
1995         3057       1067 
1996         2980       1053 
1997         1863        643 
1998        21694       9222 
1999        13536       5192 
2000        38628      15970 
2001        39460      15328 
2002        32275      14297 
2003        57779      24041 
2004        46358      17786 
2005        81448      25072 
2006       105144      33746 
2007       191937      59322 
2008       112500      32210 
2009        93258      26287 
2010       141302      38144 
2011       158343      43918 
2012       149552      41436 
2013       221522      63107 
2014       564858     143907 
2015       798401     210112 
2016       659641     171422 
2017       555060     150253 
2018       352088      98910 
2019       864423     211007 
2020       617864     157249 
2021       831845     197530 
2022       621230     177816 
2023       559204     159944 
2024       617687     177958 
2025       211856      60570