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          228         81 
1991          867        310 
1992          716        291 
1993         1264        471 
1994         1616        595 
1995         2825        989 
1996         2832       1003 
1997         2828        966 
1998        24504      10308 
1999        13346       5093 
2000        37506      15458 
2001        43030      16923 
2002        40193      16852 
2003        59343      24275 
2004        46469      17729 
2005       310572     139614 
2006       336880     150193 
2007       196508      60782 
2008       114030      32614 
2009        95255      26726 
2010       145217      38708 
2011       152989      41795 
2012       181225      39945 
2013       238796      60529 
2014       533838     130973 
2015       764474     199398 
2016       618471     159651 
2017       531245     144388 
2018       323217      90960 
2019       829650     202717 
2020       555451     140711 
2021       758884     178495 
2022       582940     166993 
2023       531214     152090 
2024       577014     165807 
2025       567950     162374 
2026        91068      24175