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        37540      15474 
2001        43067      16940 
2002        40230      16868 
2003        59406      24302 
2004        46511      17744 
2005       310762     139674 
2006       337047     150247 
2007       196657      60823 
2008       114325      32692 
2009        95589      26815 
2010       145539      38793 
2011       153405      41908 
2012       181714      40082 
2013       239428      60704 
2014       534591     131151 
2015       765740     199735 
2016       619124     159807 
2017       532647     144732 
2018       323951      91164 
2019       830711     202965 
2020       557211     141161 
2021       761622     179183 
2022       584431     167417 
2023       532253     152385 
2024       578744     166308 
2025       570475     162932 
2026        68087      19072