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          735        298 
1993         1288        480 
1994         1655        608 
1995         2956       1033 
1996         2950       1043 
1997         1813        628 
1998        21566       9177 
1999        13079       5034 
2000        38292      15824 
2001        39181      15214 
2002        30688      13741 
2003        57238      23832 
2004        45916      17627 
2005        80613      24833 
2006       103971      33409 
2007       190255      58874 
2008       110288      31621 
2009        91648      25850 
2010       143566      38593 
2011       154793      42967 
2012       146444      40604 
2013       217959      62136 
2014       559668     142630 
2015       798873     210131 
2016       655445     170294 
2017       550471     148978 
2018       346512      97379 
2019       858828     209583 
2020       609071     154927 
2021       819218     194356 
2022       614505     175914 
2023       554009     158512 
2024       608546     175339 
2025       351812     100806