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          492        186 
1992          770        310 
1993         1356        504 
1994         1752        642 
1995         3318       1154 
1996         3425       1204 
1997         2291        783 
1998        23133       9758 
1999        14447       5538 
2000        40065      16614 
2001        40921      15943 
2002        32701      14551 
2003        60085      24949 
2004        47436      18198 
2005        83426      25665 
2006       107733      34505 
2007       197970      60947 
2008       119434      34069 
2009        98145      27623 
2010       113170      31514 
2011       167663      46430 
2012       157903      43719 
2013       235313      66935 
2014       577531     147363 
2015       698559     184377 
2016       673926     174502 
2017       575523     155433 
2018       372670     104563 
2019       897999     219536 
2020       649187     165586 
2021       867890     206925 
2022       643204     184156 
2023       587212     168102 
2024       450062     131193