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        37513      15461 
2001        43037      16926 
2002        40213      16860 
2003        59372      24287 
2004        46472      17730 
2005       310609     139626 
2006       336944     150213 
2007       196579      60801 
2008       114109      32634 
2009        95325      26744 
2010       145316      38734 
2011       153087      41821 
2012       181347      39978 
2013       238965      60577 
2014       534452     131123 
2015       765073     199557 
2016       618542     159663 
2017       531518     144451 
2018       323513      91043 
2019       829878     202769 
2020       556249     140895 
2021       760023     178768 
2022       583249     167081 
2023       531506     152174 
2024       577377     165912 
2025       569477     162810 
2026        90969      24211