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         2816        986 
1996         2823       1000 
1997         2816        962 
1998        24484      10300 
1999        13329       5087 
2000        37448      15433 
2001        42949      16893 
2002        40109      16817 
2003        59225      24238 
2004        46379      17693 
2005       310458     139572 
2006       336732     150142 
2007       196306      60730 
2008       113842      32564 
2009        94988      26657 
2010       144926      38633 
2011       152635      41702 
2012       180765      39825 
2013       238431      60431 
2014       533134     130797 
2015       763816     199207 
2016       618259     159591 
2017       530444     144164 
2018       322597      90787 
2019       829479     202689 
2020       554465     140499 
2021       757240     178093 
2022       582325     166818 
2023       530694     151945 
2024       576451     165613 
2025       571751     162311 
2026        94608      25229