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         2801        981 
1996         2814        997 
1997         2789        953 
1998        24447      10288 
1999        13271       5065 
2000        37295      15362 
2001        42776      16815 
2002        39908      16732 
2003        59190      24198 
2004        46178      17610 
2005       309381     139156 
2006       335759     149762 
2007       195616      60554 
2008       112526      32207 
2009        93456      26237 
2010       141687      37834 
2011       150890      41221 
2012       178534      39218 
2013       235412      59589 
2014       533630     131069 
2015       760253     198310 
2016       626944     162024 
2017       526946     143280 
2018       317852      89496 
2019       825744     201832 
2020       546354     138396 
2021       745221     174802 
2022       575424     164852 
2023       524969     150317 
2024       569735     163703 
2025       553978     156812 
2026       222530      45117