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          719        292 
1993         1273        474 
1994         1628        599 
1995         2863       1002 
1996         2883       1020 
1997         2921        997 
1998        24659      10363 
1999        13465       5137 
2000        37838      15609 
2001        43327      17056 
2002        40562      17011 
2003        60397      24681 
2004        47061      17954 
2005       312460     140335 
2006       338561     150820 
2007       198423      61309 
2008       116214      33204 
2009        97449      27313 
2010       147642      39323 
2011       157067      42891 
2012       185156      41019 
2013       243508      61828 
2014       560519     137308 
2015       810888     209777 
2016       631637     162839 
2017       544112     147488 
2018       331530      93187 
2019       841442     205483 
2020       577070     146135 
2021       787799     185876 
2022       598094     171233 
2023       540516     154657 
2024       593661     170578 
2025       602932     171696