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          719        292 
1993         1273        474 
1994         1628        599 
1995         2854        999 
1996         2868       1015 
1997         2873        981 
1998        24600      10341 
1999        13449       5130 
2000        37742      15567 
2001        43274      17033 
2002        40479      16975 
2003        60240      24619 
2004        46955      17916 
2005       312200     140222 
2006       338330     150718 
2007       198241      61260 
2008       115900      33117 
2009        97254      27260 
2010       147549      39299 
2011       156749      42807 
2012       184854      40933 
2013       243196      61743 
2014       549396     134835 
2015       795495     206337 
2016       626646     161655 
2017       542320     147204 
2018       330829      92991 
2019       841220     205548 
2020       574798     145644 
2021       785892     185401 
2022       596714     170849 
2023       539988     154507 
2024       591876     170082 
2025       615149     175704 
2026           49          9