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          746        302 
1993         1308        487 
1994         1684        618 
1995         3096       1080 
1996         2980       1053 
1997         1869        645 
1998        22159       9378 
1999        13578       5209 
2000        38743      16019 
2001        39522      15354 
2002        32424      14353 
2003        57942      24108 
2004        46519      17848 
2005        81754      25164 
2006       105406      33824 
2007       192464      59466 
2008       113632      32511 
2009        93980      26480 
2010       120838      33281 
2011       159634      44265 
2012       150891      41807 
2013       223428      63641 
2014       568566     144837 
2015       810953     212592 
2016       664358     172342 
2017       557422     150708 
2018       354699      99624 
2019       870127     212388 
2020       622525     158484 
2021       840138     199715 
2022       626447     179298 
2023       562679     160921 
2024       626403     180395 
2025       189399      53917