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         1604        591 
1995         2804        982 
1996         2814        997 
1997         2795        955 
1998        24450      10289 
1999        13274       5066 
2000        37298      15363 
2001        42780      16817 
2002        39914      16735 
2003        59194      24200 
2004        46187      17613 
2005       309401     139163 
2006       335785     149774 
2007       195620      60555 
2008       112571      32220 
2009        93531      26258 
2010       141716      37841 
2011       150915      41228 
2012       178609      39238 
2013       235521      59620 
2014       533392     130989 
2015       760414     198354 
2016       626896     162009 
2017       526856     143267 
2018       318458      89605 
2019       825551     201764 
2020       546461     138425 
2021       745469     174870 
2022       575685     164926 
2023       525163     150372 
2024       569871     163742 
2025       554158     156863 
2026       221112      44696