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        38469      15903 
2001        39288      15261 
2002        32213      14263 
2003        57514      23940 
2004        46161      17719 
2005        80933      24929 
2006       104441      33547 
2007       190993      59073 
2008       111461      31935 
2009        92349      26044 
2010       144607      38862 
2011       156475      43427 
2012       147885      40996 
2013       219522      62570 
2014       563605     143649 
2015       797931     210074 
2016       656557     170645 
2017       553313     149778 
2018       349981      98337 
2019       861498     210327 
2020       614924     156494 
2021       827084     196392 
2022       618354     176993 
2023       557623     159427 
2024       614032     176901 
2025       237513      67967