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          713        290 
1993         1261        470 
1994         1602        590 
1995         2801        981 
1996         2814        997 
1997         2789        953 
1998        24445      10287 
1999        13271       5065 
2000        37293      15361 
2001        42776      16815 
2002        39908      16732 
2003        59184      24195 
2004        46175      17609 
2005       309353     139146 
2006       335751     149760 
2007       195605      60551 
2008       112495      32199 
2009        93425      26230 
2010       141665      37828 
2011       150858      41212 
2012       178501      39210 
2013       235352      59573 
2014       533789     131120 
2015       760073     198271 
2016       626910     162014 
2017       526985     143283 
2018       316520      89271 
2019       824779     201737 
2020       546286     138380 
2021       745074     174765 
2022       575238     164799 
2023       524837     150280 
2024       569649     163681 
2025       553927     156798 
2026       225462      45929