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         1658        609 
1995         2991       1045 
1996         2953       1044 
1997         1819        630 
1998        21582       9184 
1999        13129       5051 
2000        38409      15876 
2001        39244      15242 
2002        30769      13776 
2003        57428      23907 
2004        46077      17688 
2005        80786      24887 
2006       104231      33486 
2007       190735      59004 
2008       111055      31827 
2009        92080      25969 
2010       144213      38758 
2011       155871      43263 
2012       147346      40848 
2013       218863      62388 
2014       562476     143355 
2015       799522     210281 
2016       656111     170468 
2017       551882     149421 
2018       348865      98032 
2019       860629     210091 
2020       612957     155974 
2021       824077     195612 
2022       616508     176480 
2023       555634     158963 
2024       612166     176356 
2025       286156      82352