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         1661        610 
1995         2994       1046 
1996         2953       1044 
1997         1822        631 
1998        21587       9186 
1999        13144       5056 
2000        38420      15881 
2001        39248      15244 
2002        32671      14412 
2003        57457      23917 
2004        46091      17693 
2005        80844      24904 
2006       104300      33506 
2007       190843      59033 
2008       111154      31853 
2009        92177      25996 
2010       144311      38784 
2011       156073      43317 
2012       147507      40890 
2013       219092      62453 
2014       562786     143437 
2015       798751     210163 
2016       656109     170497 
2017       551987     149454 
2018       349201      98125 
2019       860728     210118 
2020       613504     156121 
2021       824906     195817 
2022       617019     176627 
2023       556063     159079 
2024       612884     176543 
2025       287065      82605