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         1264        471 
1994         1610        593 
1995         2819        987 
1996         2823       1000 
1997         2819        963 
1998        24484      10300 
1999        13338       5090 
2000        37450      15434 
2001        42951      16894 
2002        40111      16818 
2003        59227      24239 
2004        46395      17699 
2005       310481     139579 
2006       336738     150144 
2007       196332      60737 
2008       113858      32568 
2009        95034      26669 
2010       144940      38637 
2011       152662      41709 
2012       180789      39831 
2013       238464      60440 
2014       533181     130805 
2015       763739     199192 
2016       617826     159475 
2017       530501     144178 
2018       322637      90798 
2019       828794     202497 
2020       554414     140482 
2021       757307     178110 
2022       582423     166846 
2023       530773     151965 
2024       576311     165604 
2025       567011     162101 
2026        92898      24737