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         3069       1071 
1996         2980       1053 
1997         1863        643 
1998        21781       9251 
1999        13553       5195 
2000        38654      15980 
2001        39470      15332 
2002        32282      14300 
2003        57789      24046 
2004        46374      17792 
2005        81503      25089 
2006       105195      33761 
2007       191984      59336 
2008       112634      32246 
2009        93376      26315 
2010       138282      37455 
2011       158515      43963 
2012       149769      41495 
2013       221752      63174 
2014       565271     144005 
2015       798391     210102 
2016       659992     171521 
2017       555615     150411 
2018       352583      99052 
2019       865515     211278 
2020       618605     157457 
2021       833327     197904 
2022       621964     178031 
2023       559635     160070 
2024       618589     178212 
2025       205709      58782