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         4329       1494 
1996         3593       1262 
1997         2334        796 
1998        23309       9826 
1999        14583       5594 
2000        40633      16869 
2001        41643      16241 
2002        32763      14642 
2003        61700      25572 
2004        48471      18596 
2005        86527      26584 
2006       112023      35767 
2007       206569      63268 
2008       127513      36252 
2009       103798      29148 
2010       120446      33422 
2011       181290      50125 
2012       168368      46579 
2013       261707      74223 
2014       648413     165366 
2015       753627     199994 
2016       577859     154221 
2017       611084     163300 
2018       407812     114273 
2019       932648     227396 
2020       701864     180274 
2021       910838     218607 
2022       679629     194394 
2023       617846     177829 
2024       139886      40104