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        37900      15637 
2001        43385      17082 
2002        40629      17040 
2003        60501      24721 
2004        47161      17990 
2005       312805     140479 
2006       339058     151034 
2007       198692      61383 
2008       116693      33336 
2009        97732      27385 
2010       147952      39404 
2011       157598      43036 
2012       185814      41200 
2013       244362      62070 
2014       562267     137770 
2015       812153     210128 
2016       633411     163359 
2017       545652     147790 
2018       332853      93562 
2019       844458     206323 
2020       581284     147291 
2021       792343     187166 
2022       601039     172069 
2023       542532     155250 
2024       598135     171867 
2025       582661     166353