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          824        328 
1993         1663        608 
1994         2320        837 
1995         3368       1171 
1996         3576       1256 
1997         2326        793 
1998        23250       9803 
1999        14522       5568 
2000        40452      16785 
2001        43016      16680 
2002        32466      14512 
2003        61163      25358 
2004        47941      18387 
2005        85251      26212 
2006       110730      35382 
2007       203781      62504 
2008       125002      35581 
2009       101639      28566 
2010       118146      32818 
2011       177118      48982 
2012       164443      45469 
2013       255125      72162 
2014       605108     154939 
2015       730592     193747 
2016       704869     182101 
2017       601099     162163 
2018       395623     110843 
2019       929950     228056 
2020       685123     175535 
2021       893792     213948 
2022       663721     189836 
2023       602730     173538 
2024       244856      70891