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          716        291 
1993         1267        472 
1994         1616        595 
1995         2840        994 
1996         2847       1008 
1997         2861        977 
1998        24577      10333 
1999        13423       5121 
2000        37673      15538 
2001        43225      17012 
2002        40410      16948 
2003        60037      24537 
2004        46817      17867 
2005       311654     140010 
2006       337947     150566 
2007       197873      61158 
2008       115331      32965 
2009        96630      27094 
2010       147161      39198 
2011       155901      42577 
2012       183995      40703 
2013       241942      61409 
2014       541389     132919 
2015       771804     201350 
2016       623979     161058 
2017       539597     146610 
2018       328730      92472 
2019       838025     204767 
2020       569410     144226 
2021       779110     183548 
2022       589769     168918 
2023       536887     153653 
2024       586946     168683 
2025       603388     172470 
2026        52067      14518