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         1613        594 
1995         2825        989 
1996         2832       1003 
1997         2828        966 
1998        24504      10308 
1999        13346       5093 
2000        37494      15453 
2001        43021      16920 
2002        40176      16844 
2003        59327      24268 
2004        46460      17725 
2005       310547     139606 
2006       336829     150174 
2007       196449      60767 
2008       113980      32601 
2009        95167      26703 
2010       145139      38688 
2011       152853      41759 
2012       181168      39930 
2013       238683      60498 
2014       533604     130914 
2015       764333     199356 
2016       618281     159601 
2017       531004     144321 
2018       323061      90918 
2019       829242     202616 
2020       554814     140595 
2021       758279     178352 
2022       582763     166943 
2023       531046     152043 
2024       576789     165743 
2025       567745     162315 
2026        91052      24173