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         1483        547 
1994         2317        836 
1995         3365       1170 
1996         3576       1256 
1997         2326        793 
1998        23250       9803 
1999        14520       5567 
2000        40436      16778 
2001        42993      16672 
2002        32451      14505 
2003        61101      25334 
2004        47903      18372 
2005        85122      26172 
2006       110573      35336 
2007       203487      62425 
2008       124715      35503 
2009       101287      28470 
2010       117878      32748 
2011       176532      48819 
2012       164017      45353 
2013       254159      71891 
2014       604211     154699 
2015       729310     193403 
2016       714053     184466 
2017       600624     162042 
2018       395444     110808 
2019       928800     228026 
2020       683223     175009 
2021       892638     213648 
2022       662752     189557 
2023       601501     173188 
2024       242043      70060