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          716        291 
1993         1264        471 
1994         1616        595 
1995         2825        989 
1996         2832       1003 
1997         2828        966 
1998        24510      10310 
1999        13346       5093 
2000        37515      15462 
2001        43043      16929 
2002        40213      16860 
2003        59384      24292 
2004        46477      17732 
2005       310646     139639 
2006       336971     150223 
2007       196590      60804 
2008       114156      32646 
2009        95384      26760 
2010       145377      38750 
2011       153148      41837 
2012       181443      40005 
2013       239043      60598 
2014       534602     131161 
2015       765268     199612 
2016       618636     159682 
2017       531685     144498 
2018       323635      91075 
2019       830124     202813 
2020       556461     140954 
2021       760404     178858 
2022       583433     167135 
2023       531620     152205 
2024       577618     165982 
2025       569544     162828 
2026        88526      23544