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          815        325 
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        43016      16680 
2002        32466      14512 
2003        61160      25357 
2004        47941      18387 
2005        85243      26210 
2006       110727      35381 
2007       203771      62501 
2008       124969      35572 
2009       101626      28562 
2010       118146      32818 
2011       177098      48977 
2012       164436      45467 
2013       255082      72149 
2014       605074     154930 
2015       730546     193735 
2016       705457     182255 
2017       601062     162153 
2018       395590     110834 
2019       929814     228021 
2020       685051     175514 
2021       893747     213935 
2022       663673     189823 
2023       603044     173601 
2024       244633      70826