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        24504      10308 
1999        13346       5093 
2000        37510      15460 
2001        43037      16926 
2002        40213      16860 
2003        59372      24287 
2004        46472      17730 
2005       310604     139624 
2006       336939     150211 
2007       196575      60800 
2008       114097      32631 
2009        95318      26742 
2010       145308      38732 
2011       153087      41821 
2012       181328      39973 
2013       238942      60571 
2014       534433     131118 
2015       765057     199554 
2016       618518     159658 
2017       531428     144437 
2018       323490      91036 
2019       829832     202764 
2020       556217     140886 
2021       759957     178749 
2022       583240     167078 
2023       531461     152161 
2024       577351     165904 
2025       569466     162807 
2026        90831      24152