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        21954       9309 
1999        13562       5203 
2000        38678      15990 
2001        39480      15337 
2002        46638      19087 
2003        57823      24060 
2004        46407      17805 
2005        81577      25111 
2006       105245      33775 
2007       192117      59372 
2008       112841      32300 
2009        93535      26358 
2010       133290      36267 
2011       158723      44019 
2012       149986      41556 
2013       222114      63277 
2014       565760     144135 
2015       798666     210109 
2016       659149     171225 
2017       554784     150206 
2018       352990      99167 
2019       866481     211525 
2020       619555     157715 
2021       834918     198273 
2022       623104     178351 
2023       560590     160343 
2024       621685     179089 
2025       206667      59074