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          444        170 
1992          721        293 
1993         1283        478 
1994         1631        600 
1995         2903       1015 
1996         2895       1024 
1997         1787        619 
1998        21454       9129 
1999        12875       4962 
2000        38009      15698 
2001        39351      15255 
2002        32800      14420 
2003        56355      23491 
2004        45369      17433 
2005        79972      24644 
2006       102945      33106 
2007       187754      58202 
2008       106536      30612 
2009        89472      25264 
2010       141590      38080 
2011       150886      41903 
2012       141905      39370 
2013       215124      61347 
2014       547658     139417 
2015       795404     209313 
2016       645929     167717 
2017       544543     147388 
2018       338730      95240 
2019       851564     207898 
2020       593566     150607 
2021       803925     190248 
2022       608766     174268 
2023       548570     156990 
2024       608233     174521 
2025       531875     151974