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          540        203 
1992          942        370 
1993         1694        619 
1994         2366        854 
1995         4512       1558 
1996         3618       1271 
1997         2382        814 
1998        23451       9882 
1999        14743       5660 
2000        41278      17156 
2001        42424      16575 
2002        33688      15034 
2003        63071      26144 
2004        49661      19064 
2005        89456      27468 
2006       116007      36943 
2007       211749      64684 
2008       133118      37771 
2009       108822      30511 
2010       126481      35038 
2011       189996      52529 
2012       177857      49172 
2013       274902      77904 
2014       677946     173012 
2015       776811     206397 
2016       555382     149684 
2017       477881     136631 
2018       410619     115508 
2019       813158     199421 
2020       723828     186047 
2021       940896     226512 
2022       716583     205054 
2023       551484     157380