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         1267        472 
1994         1616        595 
1995         2840        994 
1996         2847       1008 
1997         2867        979 
1998        24580      10334 
1999        13429       5123 
2000        37691      15545 
2001        43234      17014 
2002        40421      16951 
2003        60064      24547 
2004        46833      17872 
2005       311904     140130 
2006       338010     150592 
2007       197912      61168 
2008       115399      32982 
2009        96661      27103 
2010       147176      39202 
2011       155955      42592 
2012       184056      40720 
2013       242043      61438 
2014       542831     133243 
2015       778480     202839 
2016       624954     161283 
2017       539758     146652 
2018       329023      92547 
2019       838290     204837 
2020       570546     144478 
2021       780042     183782 
2022       590718     169180 
2023       537371     153786 
2024       587486     168833 
2025       604149     172653 
2026        52536      14635