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       196119      60680 
2008       113602      32501 
2009        94672      26569 
2010       144745      38585 
2011       152317      41618 
2012       180354      39713 
2013       237871      60278 
2014       532696     130682 
2015       764940     199485 
2016       621817     160479 
2017       530156     144107 
2018       322038      90634 
2019       829574     202814 
2020       553753     140338 
2021       755740     177669 
2022       581054     166453 
2023       529869     151713 
2024       575151     165265 
2025       570273     162110 
2026       133726      35294