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         1616        595 
1995         2825        989 
1996         2832       1003 
1997         2831        967 
1998        24510      10310 
1999        13353       5096 
2000        37525      15467 
2001        43053      16934 
2002        40220      16863 
2003        59395      24297 
2004        46482      17734 
2005       310699     139655 
2006       337011     150236 
2007       196621      60813 
2008       114205      32660 
2009        95452      26779 
2010       145460      38772 
2011       153251      41865 
2012       181526      40028 
2013       239136      60624 
2014       534664     131175 
2015       765411     199651 
2016       618848     159734 
2017       531944     144570 
2018       323750      91107 
2019       830336     202871 
2020       556761     141039 
2021       760861     178976 
2022       583837     167246 
2023       531889     152280 
2024       578005     166095 
2025       570227     162866 
2026        75090      20935