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          740        300 
1993         1296        483 
1994         1664        611 
1995         3000       1048 
1996         2959       1046 
1997         1822        631 
1998        21599       9190 
1999        13171       5066 
2000        38473      15905 
2001        39288      15261 
2002        32217      14265 
2003        57521      23943 
2004        46161      17719 
2005        80933      24929 
2006       104465      33554 
2007       191008      59077 
2008       111489      31943 
2009        92359      26047 
2010       144623      38866 
2011       156519      43439 
2012       147902      41001 
2013       219544      62576 
2014       563636     143657 
2015       797976     210087 
2016       656601     170656 
2017       553357     149794 
2018       350021      98348 
2019       861545     210340 
2020       614970     156507 
2021       827296     196431 
2022       618586     177036 
2023       557891     159448 
2024       614115     176914 
2025       226783      64831