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        60249      24623 
2004        46964      17919 
2005       312205     140224 
2006       338340     150721 
2007       198248      61262 
2008       115908      33119 
2009        97254      27260 
2010       147560      39302 
2011       156757      42809 
2012       184854      40933 
2013       243250      61755 
2014       559624     137077 
2015       809108     209299 
2016       630225     162452 
2017       542755     147285 
2018       330968      93031 
2019       841558     205606 
2020       575888     145881 
2021       786748     185601 
2022       597292     171005 
2023       540186     154562 
2024       592501     170243 
2025       617674     176198 
2026            4          0