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          705        287 
1993         1261        470 
1994         1599        589 
1995         2797        980 
1996         2814        997 
1997         2789        953 
1998        24439      10285 
1999        13254       5060 
2000        37286      15358 
2001        42770      16812 
2002        39890      16726 
2003        59176      24192 
2004        46152      17601 
2005       309302     139131 
2006       335715     149747 
2007       195559      60539 
2008       112436      32182 
2009        93334      26202 
2010       141595      37808 
2011       150758      41185 
2012       178376      39176 
2013       235241      59542 
2014       533685     131094 
2015       759804     198199 
2016       626774     161982 
2017       526683     143207 
2018       315622      89100 
2019       824372     201730 
2020       547241     138659 
2021       744730     174674 
2022       574962     164724 
2023       524602     150213 
2024       569324     163592 
2025       551656     156254 
2026       225234      45871