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         2887       1010 
1996         2886       1021 
1997         2927        999 
1998        24682      10373 
1999        13491       5146 
2000        37906      15640 
2001        43406      17090 
2002        40650      17049 
2003        60516      24728 
2004        47214      18009 
2005        85851      27199 
2006       120981      42036 
2007       198922      61448 
2008       117150      33461 
2009        97931      27438 
2010       148250      39476 
2011       158155      43193 
2012       186403      41360 
2013       245014      62247 
2014       563450     138093 
2015       813335     210448 
2016       634998     163809 
2017       545871     147835 
2018       334160      93928 
2019       845879     206706 
2020       583881     147941 
2021       794513     187784 
2022       602237     172412 
2023       543440     155506 
2024       600085     172420 
2025       578320     164999