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          465        177 
1992          730        296 
1993         1283        478 
1994         1643        604 
1995         2924       1022 
1996         2921       1033 
1997         1801        624 
1998        21498       9146 
1999        12972       4996 
2000        38139      15759 
2001        39203      15212 
2002        32321      14273 
2003        56869      23687 
2004        45638      17530 
2005        80295      24739 
2006       103486      33264 
2007       189094      58563 
2008       108669      31187 
2009        90728      25602 
2010       142520      38321 
2011       152941      42459 
2012       144336      40029 
2013       216628      61776 
2014       554251     141171 
2015       794065     208854 
2016       650776     169025 
2017       547079     148070 
2018       342665      96319 
2019       854229     208412 
2020       601458     152826 
2021       811482     192289 
2022       611423     175038 
2023       551622     157857 
2024       611338     175558 
2025       441553     125374