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        37551      15479 
2001        43080      16946 
2002        40230      16868 
2003        59412      24304 
2004        46522      17748 
2005       310772     139678 
2006       337064     150252 
2007       196672      60827 
2008       114358      32701 
2009        95626      26825 
2010       145572      38802 
2011       153460      41923 
2012       181801      40106 
2013       239551      60738 
2014       534535     131136 
2015       765309     199614 
2016       619256     159841 
2017       532819     144780 
2018       324014      91182 
2019       830866     202998 
2020       557448     141207 
2021       762029     179271 
2022       584760     167511 
2023       532396     152424 
2024       578992     166378 
2025       570602     162940 
2026        60067      16833