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        40701      16902 
2001        41760      16290 
2002        32913      14700 
2003        61902      25658 
2004        48619      18657 
2005        86884      26689 
2006       112586      35932 
2007       207551      63535 
2008       128406      36493 
2009       104425      29322 
2010       121353      33662 
2011       182896      50562 
2012       169603      46917 
2013       264426      74984 
2014       657783     167685 
2015       771705     204315 
2016       578646     154299 
2017       595283     159064 
2018       407049     114175 
2019       931468     227427 
2020       712138     182805 
2021      1057572     249678 
2022       691132     197611 
2023       625264     179898 
2024       102445      29656