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          773        311 
1993         1663        608 
1994         2320        837 
1995         3368       1171 
1996         3576       1256 
1997         2326        793 
1998        23250       9803 
1999        14522       5568 
2000        40450      16784 
2001        43012      16678 
2002        32466      14512 
2003        61146      25352 
2004        47924      18380 
2005        85239      26209 
2006       110700      35373 
2007       203727      62489 
2008       124921      35559 
2009       101581      28550 
2010       118103      32807 
2011       176997      48949 
2012       164365      45448 
2013       254921      72105 
2014       604945     154896 
2015       730459     193708 
2016       709482     183201 
2017       600889     162109 
2018       395768     110889 
2019       928803     227863 
2020       684851     175457 
2021       893507     213877 
2022       663535     189785 
2023       602886     173555 
2024       244729      70857