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         3315       1153 
1996         3419       1202 
1997         2291        783 
1998        23133       9758 
1999        14447       5538 
2000        40065      16614 
2001        40915      15940 
2002        32699      14550 
2003        60083      24948 
2004        47434      18197 
2005        83413      25661 
2006       107722      34502 
2007       197962      60945 
2008       119426      34067 
2009        98124      27617 
2010       113146      31508 
2011       167645      46425 
2012       157903      43719 
2013       235290      66929 
2014       577480     147351 
2015       698508     184366 
2016       673839     174481 
2017       575480     155421 
2018       372582     104536 
2019       897908     219513 
2020       649144     165576 
2021       867849     206914 
2022       643181     184149 
2023       587209     168093 
2024       449975     131161