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        59351      24278 
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       181221      39944 
2013       238800      60530 
2014       533953     130998 
2015       764478     199399 
2016       618463     159648 
2017       531230     144384 
2018       323232      90964 
2019       829643     202715 
2020       555454     140712 
2021       758890     178497 
2022       582944     166994 
2023       531221     152092 
2024       577014     165807 
2025       567964     162378 
2026        91089      24180