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          471        179 
1992          749        303 
1993         1310        488 
1994         1689        620 
1995         3111       1085 
1996         2993       1058 
1997         1917        661 
1998        22337       9439 
1999        13620       5227 
2000        38867      16076 
2001        39653      15412 
2002        31053      13913 
2003        58227      24220 
2004        46755      17946 
2005        82164      25284 
2006       105896      33969 
2007       193570      59764 
2008       115341      32958 
2009        95040      26770 
2010       114188      31699 
2011       161683      44824 
2012       152982      42379 
2013       225679      64270 
2014       568906     145012 
2015       795393     208291 
2016       664428     172326 
2017       560658     151633 
2018       358723     100736 
2019       875935     213872 
2020       628707     160121 
2021       848608     201947 
2022       632182     180959 
2023       570178     162923 
2024       635083     182872 
2025       121161      34432