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          933        366 
1993         1663        608 
1994         2320        837 
1995         3368       1171 
1996         3576       1256 
1997         2329        794 
1998        23255       9805 
1999        14522       5568 
2000        40463      16790 
2001        43022      16683 
2002        32472      14515 
2003        61188      25367 
2004        47953      18391 
2005        85313      26231 
2006       110774      35396 
2007       203908      62538 
2008       125063      35598 
2009       101712      28586 
2010       118235      32841 
2011       177270      49025 
2012       164530      45492 
2013       255426      72249 
2014       605405     155012 
2015       730856     193814 
2016       681279     176485 
2017       602327     162336 
2018       395829     110900 
2019       930925     228221 
2020       685549     175654 
2021       894168     214034 
2022       663803     189869 
2023       603146     173651 
2024       224376      64877