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          713        290 
1993         1261        470 
1994         1604        591 
1995         2804        982 
1996         2814        997 
1997         2798        956 
1998        24464      10294 
1999        13290       5072 
2000        37305      15366 
2001        42800      16825 
2002        39938      16739 
2003        59232      24215 
2004        46204      17620 
2005       309559     139221 
2006       335874     149811 
2007       195680      60571 
2008       112755      32270 
2009        93798      26331 
2010       141801      37865 
2011       151092      41276 
2012       178809      39292 
2013       235906      59729 
2014       534406     131218 
2015       760687     198375 
2016       626200     161811 
2017       526761     143206 
2018       318832      89708 
2019       825881     201841 
2020       547184     138586 
2021       746377     175135 
2022       576613     165194 
2023       525749     150539 
2024       570265     163870 
2025       555181     157072 
2026       212579      41872