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        59354      24279 
2004        46469      17729 
2005       310572     139614 
2006       336880     150193 
2007       196508      60782 
2008       114030      32614 
2009        95259      26727 
2010       145217      38708 
2011       153000      41798 
2012       181223      39945 
2013       238800      60530 
2014       533976     131004 
2015       764509     199408 
2016       618364     159618 
2017       531136     144353 
2018       323235      90965 
2019       829596     202700 
2020       555467     140716 
2021       758967     178519 
2022       582981     167005 
2023       531240     152098 
2024       577036     165814 
2025       567994     162387 
2026        90873      24160