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         2831        991 
1996         2841       1006 
1997         2849        973 
1998        24552      10325 
1999        13375       5104 
2000        37605      15506 
2001        43174      16988 
2002        40325      16914 
2003        59552      24363 
2004        46639      17798 
2005       311075     139791 
2006       337371     150360 
2007       197086      60936 
2008       114755      32809 
2009        96043      26937 
2010       145984      38909 
2011       154316      42155 
2012       182550      40308 
2013       240485      60997 
2014       537208     131815 
2015       767436     200182 
2016       620961     160277 
2017       534734     145305 
2018       325492      91587 
2019       833835     203641 
2020       561668     142221 
2021       767029     180451 
2022       586231     167931 
2023       534068     152899 
2024       581137     167010 
2025       568560     162329 
2026        53828      15000