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        14613       5607 
2000        40715      16908 
2001        41769      16293 
2002        32919      14703 
2003        61908      25660 
2004        48619      18657 
2005        86902      26693 
2006       112596      35935 
2007       207554      63536 
2008       128414      36495 
2009       104433      29324 
2010       121364      33665 
2011       182902      50564 
2012       169617      46921 
2013       264444      74989 
2014       658265     167789 
2015       771778     204335 
2016       578206     154183 
2017       593629     158668 
2018       406844     114119 
2019       930776     227289 
2020       712234     182831 
2021       924289     222289 
2022       691325     197661 
2023       624888     179821 
2024       102437      29654