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        24580      10334 
1999        13426       5122 
2000        37679      15539 
2001        43231      17013 
2002        40413      16948 
2003        60037      24537 
2004        46826      17870 
2005       311869     140116 
2006       337973     150578 
2007       197873      61158 
2008       115356      32971 
2009        96633      27095 
2010       147165      39199 
2011       155904      42578 
2012       184002      40705 
2013       241945      61410 
2014       541410     132924 
2015       771746     201338 
2016       623903     161041 
2017       539576     146604 
2018       328752      92478 
2019       837991     204757 
2020       569434     144233 
2021       779129     183553 
2022       589781     168920 
2023       536900     153657 
2024       586987     168694 
2025       603448     172486 
2026        52169      14544