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          767        309 
1993         1356        504 
1994         1749        641 
1995         3306       1150 
1996         3327       1170 
1997         2291        783 
1998        23120       9753 
1999        14432       5532 
2000        40026      16598 
2001        40870      15923 
2002        32102      14345 
2003        59978      24908 
2004        47376      18177 
2005        83243      25611 
2006       107445      34422 
2007       197365      60780 
2008       118872      33914 
2009        97811      27528 
2010       112653      31377 
2011       166811      46204 
2012       157474      43602 
2013       233540      66450 
2014       577097     147201 
2015       758309     198296 
2016       672477     174110 
2017       573603     154933 
2018       370722     104026 
2019       895088     218763 
2020       646720     164919 
2021       866045     206438 
2022       641801     183750 
2023       585626     167521 
2024       492008     142230