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        59669      24789 
2004        47257      18133 
2005        82926      25514 
2006       106959      34280 
2007       195915      60393 
2008       117632      33576 
2009        96999      27308 
2010       111557      31097 
2011       165062      45736 
2012       156179      43252 
2013       230155      65510 
2014       555192     142292 
2015       728531     191583 
2016       667451     172866 
2017       569522     153851 
2018       366350     102811 
2019       888310     216970 
2020       640144     163150 
2021       860643     204997 
2022       638599     182787 
2023       577370     165273 
2024       544912     157545