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         2831        967 
1998        24513      10311 
1999        13353       5096 
2000        37528      15468 
2001        43056      16935 
2002        40222      16864 
2003        59399      24299 
2004        46485      17735 
2005       310711     139658 
2006       337018     150238 
2007       196621      60813 
2008       114256      32673 
2009        95471      26784 
2010       145468      38774 
2011       153318      41883 
2012       181548      40034 
2013       239202      60640 
2014       534690     131176 
2015       765439     199659 
2016       618869     159740 
2017       532048     144596 
2018       323788      91117 
2019       830416     202894 
2020       556851     141064 
2021       761002     179016 
2022       583970     167283 
2023       531925     152291 
2024       578116     166128 
2025       570283     162880 
2026        70723      19750