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        24453      10290 
1999        13277       5067 
2000        37301      15364 
2001        42780      16817 
2002        39930      16736 
2003        59200      24202 
2004        46193      17616 
2005       309438     139176 
2006       335797     149779 
2007       195631      60558 
2008       112620      32233 
2009        93573      26270 
2010       141729      37845 
2011       150950      41238 
2012       178638      39246 
2013       235608      59645 
2014       533308     130962 
2015       760568     198395 
2016       626856     161993 
2017       526842     143261 
2018       318559      89633 
2019       825613     201777 
2020       546642     138476 
2021       745649     174925 
2022       575927     164996 
2023       525308     150413 
2024       569981     163768 
2025       554329     156902 
2026       219609      44259