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         2794        979 
1996         2811        996 
1997         2780        950 
1998        24429      10281 
1999        13233       5052 
2000        37254      15342 
2001        42719      16788 
2002        39853      16707 
2003        59057      24139 
2004        46077      17571 
2005       309044     139040 
2006       335532     149680 
2007       195309      60471 
2008       112161      32107 
2009        93027      26118 
2010       141239      37716 
2011       150164      41025 
2012       177874      39041 
2013       234640      59376 
2014       532389     130754 
2015       757795     197647 
2016       625658     161680 
2017       525900     143001 
2018       314623      88816 
2019       822962     201353 
2020       544913     138080 
2021       740613     173612 
2022       573238     164235 
2023       523451     149891 
2024       567285     163014 
2025       548729     155536 
2026       225849      46075