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         2825        989 
1996         2832       1003 
1997         2828        966 
1998        24510      10310 
1999        13346       5093 
2000        37513      15461 
2001        43043      16929 
2002        40213      16860 
2003        59382      24291 
2004        46477      17732 
2005       310635     139636 
2006       336967     150221 
2007       196586      60803 
2008       114144      32643 
2009        95361      26754 
2010       145357      38745 
2011       153118      41829 
2012       181398      39992 
2013       238997      60586 
2014       534554     131149 
2015       765213     199595 
2016       618601     159672 
2017       531635     144484 
2018       323601      91066 
2019       829942     202784 
2020       556392     140935 
2021       760320     178833 
2022       583347     167110 
2023       531570     152191 
2024       577500     165948 
2025       569515     162821 
2026        91250      24290