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         1599        589 
1995         2797        980 
1996         2811        996 
1997         2780        950 
1998        24429      10281 
1999        13236       5053 
2000        37263      15347 
2001        42730      16793 
2002        39866      16714 
2003        59079      24149 
2004        46097      17579 
2005       309090     139057 
2006       335566     149695 
2007       195348      60481 
2008       112174      32110 
2009        93078      26132 
2010       141288      37729 
2011       150255      41049 
2012       177949      39060 
2013       234758      59410 
2014       532511     130787 
2015       758042     197714 
2016       625770     161711 
2017       525686     142944 
2018       314760      88854 
2019       823105     201389 
2020       545362     138177 
2021       741077     173735 
2022       573573     164328 
2023       523666     149954 
2024       567575     163098 
2025       548907     155588 
2026       226165      46154