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         2813        985 
1996         2823       1000 
1997         2813        961 
1998        24484      10300 
1999        13318       5083 
2000        37440      15429 
2001        42932      16885 
2002        40100      16813 
2003        59197      24228 
2004        46358      17686 
2005       310381     139547 
2006       336701     150129 
2007       196233      60711 
2008       113728      32534 
2009        94897      26632 
2010       144874      38619 
2011       152539      41678 
2012       180541      39765 
2013       238206      60371 
2014       532951     130746 
2015       764079     199271 
2016       618171     159571 
2017       530604     144230 
2018       322431      90744 
2019       830072     202917 
2020       554097     140409 
2021       756559     177902 
2022       581795     166667 
2023       530415     151869 
2024       575827     165455 
2025       570956     162255 
2026       112738      29881