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         1267        472 
1994         1616        595 
1995         2828        990 
1996         2838       1005 
1997         2846        972 
1998        24549      10324 
1999        13366       5101 
2000        37581      15494 
2001        43132      16970 
2002        40283      16894 
2003        59506      24345 
2004        46583      17774 
2005       310929     139736 
2006       337225     150311 
2007       196876      60880 
2008       114572      32760 
2009        95864      26889 
2010       145792      38858 
2011       153903      42043 
2012       182177      40206 
2013       240078      60881 
2014       535821     131457 
2015       766088     199832 
2016       620195     160082 
2017       533740     145030 
2018       324706      91374 
2019       832223     203314 
2020       559669     141697 
2021       764551     179897 
2022       585609     167754 
2023       533224     152657 
2024       580125     166708 
2025       571318     163130 
2026        54248      15113