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         2840        970 
1998        24522      10314 
1999        13355       5097 
2000        37538      15473 
2001        43065      16939 
2002        40226      16866 
2003        59404      24301 
2004        46496      17739 
2005       310747     139669 
2006       337031     150242 
2007       196644      60819 
2008       114283      32681 
2009        95548      26804 
2010       145498      38782 
2011       153377      41900 
2012       181617      40053 
2013       239332      60677 
2014       534553     131141 
2015       765398     199648 
2016       618947     159761 
2017       532460     144679 
2018       323881      91143 
2019       830508     202908 
2020       557034     141113 
2021       761318     179096 
2022       584148     167334 
2023       532090     152338 
2024       578381     166205 
2025       570331     162894 
2026        66723      18700