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        60242      24620 
2004        46955      17916 
2005       312200     140222 
2006       338330     150718 
2007       198241      61260 
2008       115908      33119 
2009        97254      27260 
2010       147560      39302 
2011       156753      42808 
2012       184854      40933 
2013       243196      61743 
2014       551895     135391 
2015       795589     206352 
2016       626709     161668 
2017       542318     147202 
2018       330863      93000 
2019       841125     205520 
2020       575207     145693 
2021       786726     185595 
2022       597289     171004 
2023       540176     154559 
2024       592427     170223 
2025       618813     176512 
2026           35          4