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          743        301 
1993         1308        487 
1994         1684        618 
1995         3081       1075 
1996         2980       1053 
1997         1866        644 
1998        21963       9312 
1999        13562       5203 
2000        38680      15991 
2001        39480      15337 
2002        47490      19368 
2003        57824      24061 
2004        46407      17805 
2005        81580      25112 
2006       105253      33777 
2007       192141      59379 
2008       112894      32315 
2009        93578      26370 
2010       133309      36272 
2011       158772      44033 
2012       150027      41567 
2013       222151      63287 
2014       565836     144156 
2015       798633     210095 
2016       658925     171156 
2017       554722     150181 
2018       353055      99186 
2019       866630     211565 
2020       619619     157733 
2021       835105     198325 
2022       623209     178380 
2023       560661     160363 
2024       621868     179138 
2025       207338      59256