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         1607        592 
1995         2810        984 
1996         2823       1000 
1997         2804        958 
1998        24481      10299 
1999        13308       5079 
2000        37421      15420 
2001        42907      16873 
2002        40070      16800 
2003        59156      24211 
2004        46322      17672 
2005       310186     139470 
2006       336513     150054 
2007       196083      60670 
2008       113473      32466 
2009        94572      26541 
2010       144668      38564 
2011       152235      41595 
2012       180195      39671 
2013       237644      60214 
2014       533750     130955 
2015       765135     199543 
2016       624295     161247 
2017       530064     144088 
2018       321764      90553 
2019       829302     202735 
2020       553406     140246 
2021       755255     177532 
2022       580686     166349 
2023       529525     151614 
2024       574766     165153 
2025       569647     162046 
2026       360196      39259