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          468        178 
1992          737        299 
1993         1291        481 
1994         1658        609 
1995         2976       1040 
1996         2953       1044 
1997         1815        629 
1998        21580       9183 
1999        13091       5038 
2000        38348      15848 
2001        39209      15226 
2002        30734      13760 
2003        57347      23873 
2004        46009      17663 
2005        80695      24859 
2006       104132      33455 
2007       190484      58936 
2008       110721      31738 
2009        91921      25924 
2010       143873      38673 
2011       155341      43119 
2012       146950      40744 
2013       218393      62256 
2014       561334     143077 
2015       799402     210287 
2016       656175     170499 
2017       551119     149183 
2018       347757      97723 
2019       859699     209840 
2020       611287     155513 
2021       822244     195130 
2022       615594     176222 
2023       554726     158706 
2024       610108     175787 
2025       317950      90815