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         1654        605 
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        85235      26208 
2006       110700      35373 
2007       203727      62489 
2008       124902      35554 
2009       101574      28548 
2010       118089      32803 
2011       176982      48945 
2012       164353      45445 
2013       254910      72102 
2014       604914     154888 
2015       730425     193698 
2016       710404     183446 
2017       600854     162099 
2018       395820     110906 
2019       928727     227844 
2020       684846     175458 
2021       893471     213867 
2022       663498     189775 
2023       602840     173544 
2024       244578      70810