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          225         80 
1991          867        310 
1992          705        287 
1993         1261        470 
1994         1596        588 
1995         2794        979 
1996         2811        996 
1997         2780        950 
1998        24429      10281 
1999        13230       5051 
2000        37255      15343 
2001        42725      16791 
2002        39858      16710 
2003        59067      24144 
2004        46087      17575 
2005       309073     139051 
2006       335541     149684 
2007       195309      60471 
2008       112166      32108 
2009        93057      26126 
2010       141269      37724 
2011       150209      41037 
2012       177911      39050 
2013       234715      59397 
2014       532464     130774 
2015       757956     197689 
2016       625727     161697 
2017       525727     142951 
2018       314701      88837 
2019       823047     201373 
2020       545125     138131 
2021       740894     173686 
2022       573393     164278 
2023       523570     149925 
2024       567481     163070 
2025       548864     155575 
2026       225763      46048