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          489        185 
1992          767        309 
1993         1356        504 
1994         1746        640 
1995         3285       1143 
1996         3126       1103 
1997         2288        782 
1998        23078       9736 
1999        14410       5524 
2000        39958      16566 
2001        40707      15858 
2002        31958      14290 
2003        59663      24787 
2004        47257      18133 
2005        82926      25514 
2006       106959      34280 
2007       195915      60393 
2008       117626      33574 
2009        96996      27307 
2010       111557      31097 
2011       165058      45735 
2012       156175      43251 
2013       230147      65508 
2014       555192     142292 
2015       720270     189769 
2016       667448     172865 
2017       569510     153847 
2018       366350     102811 
2019       888307     216969 
2020       640133     163147 
2021       860632     204994 
2022       638599     182787 
2023       578220     165527 
2024       545219     157637