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          713        290 
1993         1261        470 
1994         1604        591 
1995         2804        982 
1996         2814        997 
1997         2795        955 
1998        24454      10291 
1999        13280       5068 
2000        37301      15364 
2001        42780      16817 
2002        39930      16736 
2003        59202      24203 
2004        46196      17617 
2005       309455     139183 
2006       335809     149785 
2007       195631      60558 
2008       112628      32235 
2009        93573      26270 
2010       141733      37846 
2011       150956      41240 
2012       178646      39248 
2013       235628      59651 
2014       533301     130960 
2015       760594     198401 
2016       626801     161972 
2017       526673     143221 
2018       318587      89641 
2019       825609     201776 
2020       546677     138486 
2021       745700     174940 
2022       575983     165013 
2023       525337     150422 
2024       569857     163755 
2025       554362     156908 
2026       220085      44222