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          219         78 
1991          864        309 
1992          675        277 
1993         1222        457 
1994         1593        587 
1995         2705        949 
1996         2802        993 
1997         2771        947 
1998        24404      10270 
1999        13179       5033 
2000        37215      15324 
2001        42247      16624 
2002        35785      15335 
2003        58465      23933 
2004        46001      17540 
2005       308716     138907 
2006       335283     149581 
2007       195042      60399 
2008       111871      32030 
2009        92686      26025 
2010       140880      37622 
2011       149734      40905 
2012       177339      38896 
2013       233846      59153 
2014       531181     130437 
2015       756213     197236 
2016       626462     161914 
2017       525337     142870 
2018       313427      88494 
2019       821708     201091 
2020       543081     137577 
2021       737291     172787 
2022       571348     163700 
2023       522111     149512 
2024       566093     162664 
2025       547970     154956 
2026       238194      49962