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          746        302 
1993         1308        487 
1994         1684        618 
1995         3084       1076 
1996         2980       1053 
1997         1866        644 
1998        22016       9330 
1999        13562       5203 
2000        38682      15992 
2001        39485      15339 
2002        64115      24904 
2003        57833      24065 
2004        46407      17805 
2005        81591      25115 
2006       105269      33782 
2007       192187      59391 
2008       112950      32330 
2009        93598      26375 
2010       133344      36282 
2011       158847      44054 
2012       150135      41597 
2013       222298      63329 
2014       566069     144216 
2015       798276     209984 
2016       658628     171058 
2017       554321     150048 
2018       353364      99275 
2019       866818     211617 
2020       619838     157796 
2021       835579     198462 
2022       623527     178473 
2023       560808     160407 
2024       622225     179235 
2025       204907      58512