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         2738        960 
1996         2811        996 
1997         2780        950 
1998        24427      10280 
1999        13233       5052 
2000        37254      15342 
2001        42715      16786 
2002        39852      16706 
2003        59057      24139 
2004        46073      17569 
2005       309028     139034 
2006       335527     149678 
2007       195302      60469 
2008       112147      32103 
2009        93017      26115 
2010       141235      37715 
2011       150146      41020 
2012       177866      39039 
2013       234597      59363 
2014       532349     130743 
2015       757738     197631 
2016       625766     161705 
2017       525888     143003 
2018       314549      88797 
2019       822882     201330 
2020       544823     138054 
2021       740490     173575 
2022       573111     164198 
2023       523380     149870 
2024       567212     162994 
2025       548679     155525 
2026       225939      46109