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         1610        593 
1995         2816        986 
1996         2823       1000 
1997         2813        961 
1998        24484      10300 
1999        13326       5086 
2000        37442      15430 
2001        42940      16889 
2002        40104      16815 
2003        59215      24235 
2004        46367      17689 
2005       310445     139568 
2006       336721     150138 
2007       196287      60725 
2008       113785      32549 
2009        94955      26648 
2010       144915      38630 
2011       152614      41697 
2012       180659      39797 
2013       238352      60411 
2014       533084     130781 
2015       764079     199268 
2016       618268     159595 
2017       530685     144246 
2018       322508      90764 
2019       829414     202675 
2020       554344     140470 
2021       757012     178029 
2022       582186     166780 
2023       530622     151925 
2024       576183     165557 
2025       571129     162302 
2026        96338      25695