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        21769       9247 
1999        13553       5195 
2000        38654      15980 
2001        39470      15332 
2002        32280      14299 
2003        57789      24046 
2004        46372      17791 
2005        81495      25086 
2006       105184      33758 
2007       191981      59335 
2008       112623      32243 
2009        93365      26312 
2010       138282      37455 
2011       158495      43958 
2012       149762      41493 
2013       221746      63172 
2014       565254     144001 
2015       798422     210113 
2016       660007     171525 
2017       555608     150408 
2018       352537      99040 
2019       865483     211267 
2020       618586     157452 
2021       833202     197882 
2022       621866     178001 
2023       559632     160069 
2024       618571     178207 
2025       205861      58831