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         1293        482 
1994         1658        609 
1995         2982       1042 
1996         2953       1044 
1997         1815        629 
1998        21580       9183 
1999        13100       5041 
2000        38368      15856 
2001        39217      15230 
2002        30742      13764 
2003        57357      23878 
2004        46039      17673 
2005        80715      24865 
2006       104147      33459 
2007       190552      58954 
2008       110806      31761 
2009        91963      25936 
2010       143916      38685 
2011       155447      43148 
2012       147011      40761 
2013       218459      62276 
2014       561475     143111 
2015       799488     210310 
2016       656326     170531 
2017       551172     149206 
2018       347912      97767 
2019       859860     209884 
2020       611607     155603 
2021       822591     195230 
2022       615686     176248 
2023       554894     158755 
2024       610354     175855 
2025       319819      91283