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          743        301 
1993         1308        487 
1994         1678        616 
1995         3051       1065 
1996         2980       1053 
1997         1860        642 
1998        21679       9217 
1999        13501       5180 
2000        38622      15967 
2001        39447      15322 
2002        32602      14405 
2003        57753      24029 
2004        46338      17778 
2005        81423      25064 
2006       105087      33728 
2007       191862      59301 
2008       112398      32183 
2009        93170      26261 
2010       141242      38127 
2011       158078      43848 
2012       149419      41398 
2013       221234      63027 
2014       564881     143917 
2015       798567     210169 
2016       659328     171343 
2017       554915     150200 
2018       351777      98821 
2019       864010     210894 
2020       617408     157128 
2021       830783     197282 
2022       620212     177520 
2023       558679     159796 
2024       617756     177979 
2025       212727      60814