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        24674      10370 
1999        13483       5143 
2000        37878      15627 
2001        43342      17063 
2002        40591      17024 
2003        60464      24707 
2004        47105      17969 
2005       312509     140352 
2006       338646     150855 
2007       198494      61328 
2008       116390      33253 
2009        97536      27337 
2010       147732      39347 
2011       157200      42929 
2012       185379      41079 
2013       243820      61918 
2014       561118     137466 
2015       811362     209906 
2016       632089     162960 
2017       544976     147657 
2018       332097      93350 
2019       842778     205854 
2020       578786     146597 
2021       789712     186433 
2022       599433     171610 
2023       541478     154933 
2024       595099     170993 
2025       600281     170851