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        13449       5130 
2000        37746      15568 
2001        43276      17034 
2002        40481      16976 
2003        60255      24625 
2004        46968      17920 
2005       312238     140240 
2006       338367     150734 
2007       198272      61269 
2008       115948      33129 
2009        97277      27266 
2010       147559      39302 
2011       156778      42815 
2012       184871      40938 
2013       243268      61760 
2014       559782     137112 
2015       810351     209630 
2016       630532     162532 
2017       543101     147290 
2018       330983      93035 
2019       841209     205449 
2020       576179     145902 
2021       786906     185625 
2022       597356     171023 
2023       540209     154568 
2024       592762     170313 
2025       618855     176522