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         1607        592 
1995         2810        984 
1996         2823       1000 
1997         2807        959 
1998        24481      10299 
1999        13308       5079 
2000        37425      15422 
2001        42911      16875 
2002        40070      16800 
2003        59156      24211 
2004        46322      17672 
2005       310203     139476 
2006       336523     150059 
2007       196087      60671 
2008       113503      32474 
2009        94587      26545 
2010       144701      38573 
2011       152243      41597 
2012       180230      39681 
2013       237706      60232 
2014       533116     130819 
2015       765210     199563 
2016       623810     161115 
2017       529898     144043 
2018       321839      90576 
2019       829363     202753 
2020       553507     140275 
2021       755402     177572 
2022       580786     166378 
2023       529594     151635 
2024       574826     165170 
2025       569834     162066 
2026       353090      38581