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          228         81 
1991          867        310 
1992          708        288 
1993         1261        470 
1994         1599        589 
1995         2797        980 
1996         2814        997 
1997         2789        953 
1998        24439      10285 
1999        13259       5062 
2000        37288      15359 
2001        42774      16814 
2002        39893      16726 
2003        59178      24193 
2004        46157      17603 
2005       309326     139137 
2006       335736     149756 
2007       195571      60542 
2008       112448      32185 
2009        93350      26207 
2010       141618      37814 
2011       150806      41198 
2012       178421      39189 
2013       235267      59549 
2014       533740     131109 
2015       759889     198222 
2016       626886     162007 
2017       526829     143246 
2018       315710      89127 
2019       824507     201772 
2020       546840     138540 
2021       744851     174705 
2022       575034     164744 
2023       524666     150231 
2024       569422     163616 
2025       551699     156632 
2026       225297      45891