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          719        292 
1993         1273        474 
1994         1628        599 
1995         2854        999 
1996         2868       1015 
1997         2876        982 
1998        24605      10343 
1999        13451       5131 
2000        37753      15570 
2001        43278      17035 
2002        40483      16977 
2003        60257      24626 
2004        46970      17921 
2005       312272     140255 
2006       338395     150748 
2007       198304      61278 
2008       115988      33141 
2009        97305      27273 
2010       147563      39303 
2011       156798      42820 
2012       184935      40956 
2013       243312      61772 
2014       559900     137142 
2015       810406     209645 
2016       630726     162585 
2017       543237     147294 
2018       331081      93064 
2019       840853     205328 
2020       576334     145937 
2021       787028     185659 
2022       597504     171064 
2023       540248     154581 
2024       592942     170368 
2025       618962     176523