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          512        193 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4425       1527 
1996         3599       1264 
1997         2337        797 
1998        23325       9833 
1999        14598       5601 
2000        40670      16887 
2001        41704      16267 
2002        32839      14672 
2003        61813      25619 
2004        48561      18633 
2005        86744      26647 
2006       112288      35845 
2007       207087      63408 
2008       127953      36369 
2009       104194      29256 
2010       120926      33549 
2011       182191      50373 
2012       169072      46774 
2013       263176      74629 
2014       654490     166881 
2015       764186     202573 
2016       578987     154432 
2017       603139     161060 
2018       406391     113981 
2019       933182     227557 
2020       709907     182202 
2021       921788     221670 
2022       689353     197114 
2023       621660     178897 
2024       118118      33819