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        13199       5040 
2000        37231      15332 
2001        42283      16640 
2002        35814      15351 
2003        58521      23957 
2004        46061      17564 
2005       308867     138970 
2006       335422     149635 
2007       195195      60441 
2008       112035      32072 
2009        92878      26077 
2010       141103      37681 
2011       150015      40983 
2012       177727      39002 
2013       234333      59288 
2014       531995     130650 
2015       757309     197515 
2016       626332     161852 
2017       525548     142932 
2018       314100      88684 
2019       822533     201250 
2020       544396     137937 
2021       739468     173355 
2022       572314     163973 
2023       522894     149730 
2024       566938     162916 
2025       548130     155393 
2026       232831      48163