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       312250     140245 
2006       338373     150737 
2007       198278      61271 
2008       115948      33129 
2009        97289      27269 
2010       147559      39302 
2011       156782      42816 
2012       184890      40943 
2013       243285      61765 
2014       559789     137114 
2015       810349     209630 
2016       630595     162550 
2017       543069     147280 
2018       330993      93038 
2019       841079     205407 
2020       576219     145913 
2021       786933     185633 
2022       597380     171030 
2023       540218     154571 
2024       592865     170347 
2025       619200     176622