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          724        294 
1993         1283        478 
1994         1640        603 
1995         2912       1018 
1996         2904       1027 
1997         1796        622 
1998        21475       9138 
1999        12936       4983 
2000        38087      15734 
2001        39772      15400 
2002        31411      13963 
2003        56600      23586 
2004        45519      17486 
2005        80132      24692 
2006       103203      33181 
2007       188421      58384 
2008       107604      30904 
2009        90109      25437 
2010       142005      38188 
2011       151918      42186 
2012       143204      39724 
2013       215802      61537 
2014       550979     140291 
2015       793622     208768 
2016       648712     168473 
2017       545509     147646 
2018       340565      95735 
2019       851740     207823 
2020       597068     151596 
2021       807630     191254 
2022       609693     174551 
2023       549957     157388 
2024       606023     174229 
2025       471875     134795