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         2838       1005 
1997         2843        971 
1998        24529      10316 
1999        13361       5099 
2000        37565      15486 
2001        43084      16948 
2002        40244      16875 
2003        59445      24319 
2004        46540      17756 
2005       310822     139696 
2006       337082     150258 
2007       196721      60840 
2008       114418      32718 
2009        95682      26840 
2010       145608      38811 
2011       153518      41938 
2012       181847      40118 
2013       239653      60763 
2014       534669     131169 
2015       764956     199533 
2016       619456     159893 
2017       533052     144838 
2018       324087      91201 
2019       831020     203037 
2020       557698     141278 
2021       762351     179367 
2022       584894     167549 
2023       532537     152463 
2024       579219     166443 
2025       570837     163003 
2026        58711      16426