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          468        178 
1992          740        300 
1993         1296        483 
1994         1658        609 
1995         2982       1042 
1996         2953       1044 
1997         1819        630 
1998        21580       9183 
1999        13100       5041 
2000        38370      15857 
2001        39219      15231 
2002        30744      13765 
2003        57366      23882 
2004        46039      17673 
2005        80721      24867 
2006       104160      33463 
2007       190566      58958 
2008       110836      31769 
2009        91986      25943 
2010       143927      38688 
2011       155474      43155 
2012       147051      40771 
2013       218482      62283 
2014       561447     143097 
2015       799374     210277 
2016       656289     170519 
2017       551126     149203 
2018       347989      97789 
2019       859892     209893 
2020       611740     155640 
2021       822733     195272 
2022       615740     176264 
2023       554926     158764 
2024       610396     175867 
2025       309311      88225