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         2873        981 
1998        24600      10341 
1999        13449       5130 
2000        37746      15568 
2001        43274      17033 
2002        40479      16975 
2003        60242      24620 
2004        46955      17916 
2005       312200     140222 
2006       338330     150718 
2007       198248      61262 
2008       115908      33119 
2009        97254      27260 
2010       147560      39302 
2011       156757      42809 
2012       184854      40933 
2013       243230      61752 
2014       551903     135393 
2015       801743     207722 
2016       630196     162444 
2017       542437     147228 
2018       330968      93031 
2019       841654     205642 
2020       575884     145885 
2021       786741     185599 
2022       597289     171004 
2023       540180     154560 
2024       592490     170240 
2025       617665     176193 
2026            4          0