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          231         82 
1991          867        310 
1992          721        293 
1993         1280        477 
1994         1628        599 
1995         2881       1008 
1996         2886       1021 
1997         2927        999 
1998        24676      10371 
1999        13483       5143 
2000        37880      15628 
2001        43355      17068 
2002        40598      17027 
2003        60472      24710 
2004        47122      17975 
2005       312534     140361 
2006       338725     150888 
2007       198556      61346 
2008       116503      33284 
2009        97579      27349 
2010       147815      39368 
2011       157343      42967 
2012       185530      41121 
2013       244026      61977 
2014       561552     137585 
2015       811666     209993 
2016       632473     163068 
2017       545221     147690 
2018       332296      93405 
2019       843911     206166 
2020       579900     146906 
2021       790762     186722 
2022       600108     171801 
2023       541845     155055 
2024       595887     171222 
2025       589246     167995