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         1273        474 
1994         1619        596 
1995         2848        997 
1996         2862       1013 
1997         2870        980 
1998        24595      10339 
1999        13441       5127 
2000        37730      15561 
2001        43250      17021 
2002        40445      16962 
2003        60129      24573 
2004        46879      17889 
2005       312027     140173 
2006       338173     150655 
2007       198098      61220 
2008       115626      33044 
2009        96997      27196 
2010       147388      39258 
2011       156405      42715 
2012       184539      40850 
2013       242778      61639 
2014       544308     133608 
2015       781439     203548 
2016       625226     161320 
2017       541728     147107 
2018       329883      92786 
2019       840364     205371 
2020       573938     145406 
2021       784494     185019 
2022       595254     170442 
2023       539395     154338 
2024       590587     169717 
2025       609630     174198 
2026        24228       6823