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       207411      63498 
2008       128188      36434 
2009       104354      29301 
2010       121212      33625 
2011       182725      50517 
2012       169408      46865 
2013       263997      74863 
2014       657257     167550 
2015       771158     204168 
2016       578355     154230 
2017       597268     159523 
2018       406677     114072 
2019       931114     227313 
2020       711586     182650 
2021       923510     222076 
2022       690595     197460 
2023       624775     179758 
2024       105610      30558