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         2810        960 
1998        24481      10299 
1999        13313       5081 
2000        37431      15425 
2001        42915      16877 
2002        40080      16805 
2003        59169      24216 
2004        46335      17677 
2005       310251     139497 
2006       336602     150090 
2007       196122      60681 
2008       113602      32501 
2009        94672      26569 
2010       144745      38585 
2011       152317      41618 
2012       180342      39710 
2013       237867      60276 
2014       532633     130661 
2015       764835     199454 
2016       621171     160310 
2017       530157     144107 
2018       322038      90634 
2019       829592     202819 
2020       553763     140341 
2021       755746     177671 
2022       581079     166460 
2023       529878     151716 
2024       575157     165267 
2025       570335     162114 
2026       133494      35219