Year Observations     Objects
1858            3          3 
1889            1          1 
1901            1          1 
1920            6          2 
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           14          7 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          219         78 
1991          864        309 
1992          675        277 
1993         1222        457 
1994         1593        587 
1995         2708        950 
1996         2802        993 
1997         2771        947 
1998        24404      10270 
1999        13179       5033 
2000        37221      15327 
2001        42256      16628 
2002        35794      15339 
2003        58483      23941 
2004        46017      17546 
2005       308723     138910 
2006       335316     149595 
2007       195071      60407 
2008       111901      32038 
2009        92746      26042 
2010       140932      37636 
2011       149744      40908 
2012       177377      38907 
2013       233972      59187 
2014       531295     130467 
2015       756361     197276 
2016       626647     161963 
2017       525463     142909 
2018       313563      88534 
2019       821864     201133 
2020       543218     137613 
2021       737546     172858 
2022       571574     163764 
2023       522213     149542 
2024       566163     162684 
2025       548312     155016 
2026       238257      49960