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          713        290 
1993         1261        470 
1994         1604        591 
1995         2804        982 
1996         2814        997 
1997         2798        956 
1998        24464      10294 
1999        13290       5072 
2000        37303      15365 
2001        42784      16819 
2002        39938      16739 
2003        59209      24206 
2004        46199      17618 
2005       309497     139198 
2006       335825     149791 
2007       195661      60566 
2008       112673      32248 
2009        93682      26299 
2010       141753      37851 
2011       151026      41259 
2012       178707      39265 
2013       235766      59690 
2014       534224     131172 
2015       761115     198492 
2016       626538     161901 
2017       526661     143215 
2018       318700      89673 
2019       825691     201795 
2020       547011     138552 
2021       745978     175019 
2022       576246     165088 
2023       525503     150470 
2024       570093     163822 
2025       554637     156967 
2026       217666      43479