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         1616        595 
1995         2828        990 
1996         2832       1003 
1997         2840        970 
1998        24525      10315 
1999        13355       5097 
2000        37553      15480 
2001        43082      16947 
2002        40232      16869 
2003        59416      24306 
2004        46526      17750 
2005       310790     139684 
2006       337072     150255 
2007       196698      60834 
2008       114375      32706 
2009        95648      26831 
2010       145591      38807 
2011       153487      41930 
2012       181807      40107 
2013       239598      60751 
2014       534600     131153 
2015       764942     199525 
2016       619270     159843 
2017       532959     144812 
2018       324027      91186 
2019       830891     203004 
2020       557544     141234 
2021       762175     179316 
2022       584817     167527 
2023       532447     152438 
2024       579082     166402 
2025       570628     162950 
2026        59324      16613