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          225         80 
1991          867        310 
1992          705        287 
1993         1261        470 
1994         1596        588 
1995         2717        953 
1996         2811        996 
1997         2774        948 
1998        24414      10275 
1999        13214       5045 
2000        37233      15333 
2001        42283      16640 
2002        35814      15351 
2003        58521      23957 
2004        46061      17564 
2005       308878     138973 
2006       335444     149643 
2007       195206      60444 
2008       112039      32073 
2009        92896      26082 
2010       141111      37683 
2011       150019      40984 
2012       177731      39003 
2013       234347      59292 
2014       532008     130654 
2015       757322     197519 
2016       626366     161862 
2017       525572     142939 
2018       314139      88695 
2019       822572     201262 
2020       544430     137947 
2021       739540     173376 
2022       572375     163991 
2023       522917     149737 
2024       566956     162922 
2025       548147     155400 
2026       231991      47915