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         2807        983 
1996         2817        998 
1997         2798        956 
1998        24467      10295 
1999        13290       5072 
2000        37319      15373 
2001        42808      16829 
2002        39947      16743 
2003        59258      24226 
2004        46209      17622 
2005       309590     139231 
2006       335898     149818 
2007       195707      60578 
2008       112823      32289 
2009        93854      26346 
2010       141833      37873 
2011       151143      41290 
2012       178851      39304 
2013       235976      59748 
2014       533942     131062 
2015       760187     198246 
2016       626019     161757 
2017       526742     143199 
2018       318958      89745 
2019       825895     201834 
2020       547523     138657 
2021       746737     175241 
2022       576865     165266 
2023       525917     150587 
2024       570542     163949 
2025       558020     157495 
2026       211713      41262