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          719        292 
1993         1273        474 
1994         1628        599 
1995         2854        999 
1996         2868       1015 
1997         2876        982 
1998        24600      10341 
1999        13451       5131 
2000        37750      15569 
2001        43276      17034 
2002        40481      16976 
2003        60255      24625 
2004        46968      17920 
2005       312266     140252 
2006       338385     150743 
2007       198278      61271 
2008       115969      33135 
2009        97297      27271 
2010       147559      39302 
2011       156786      42817 
2012       184906      40948 
2013       243289      61766 
2014       559824     137123 
2015       810377     209637 
2016       630640     162561 
2017       543169     147279 
2018       331015      93045 
2019       841009     205382 
2020       576235     145918 
2021       786945     185636 
2022       597396     171035 
2023       540239     154578 
2024       592876     170350 
2025       619234     176641