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          532        200 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4425       1527 
1996         3602       1265 
1997         2340        798 
1998        23328       9834 
1999        14611       5606 
2000        40697      16900 
2001        41750      16285 
2002        32896      14693 
2003        61872      25644 
2004        48603      18650 
2005        86846      26677 
2006       112459      35894 
2007       207407      63497 
2008       128184      36433 
2009       104354      29301 
2010       121208      33624 
2011       182721      50516 
2012       169408      46865 
2013       263986      74860 
2014       657257     167550 
2015       771158     204168 
2016       578421     154249 
2017       597978     159708 
2018       406724     114086 
2019       931411     227370 
2020       711595     182653 
2021       923447     222064 
2022       690591     197459 
2023       624520     179704 
2024       105813      30618