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        37874      15625 
2001        43342      17063 
2002        40585      17021 
2003        60456      24703 
2004        47093      17964 
2005       312487     140345 
2006       338595     150835 
2007       198446      61315 
2008       116275      33222 
2009        97466      27318 
2010       147671      39331 
2011       157120      42906 
2012       185229      41038 
2013       243576      61847 
2014       560672     137351 
2015       811031     209815 
2016       631779     162876 
2017       544511     147545 
2018       331730      93241 
2019       841678     205552 
2020       577241     146185 
2021       788013     185935 
2022       598307     171292 
2023       540660     154696 
2024       593878     170641 
2025       598577     170358