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         2813        985 
1996         2823       1000 
1997         2807        959 
1998        24481      10299 
1999        13313       5081 
2000        37431      15425 
2001        42915      16877 
2002        40078      16804 
2003        59166      24215 
2004        46331      17676 
2005       310236     139491 
2006       336582     150082 
2007       196111      60678 
2008       113551      32487 
2009        94625      26555 
2010       144719      38578 
2011       152288      41610 
2012       180288      39696 
2013       237800      60257 
2014       532885     130747 
2015       764877     199465 
2016       622522     160670 
2017       530000     144066 
2018       321983      90618 
2019       829449     202778 
2020       553631     140309 
2021       755589     177626 
2022       580902     166411 
2023       529722     151671 
2024       575063     165236 
2025       570075     162087 
2026       135514      35755