Year Observations     Objects
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           12          6 
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          216         77 
1991          856        306 
1992          656        270 
1993         1176        442 
1994         1490        556 
1995         2368        836 
1996         2631        934 
1997         2509        857 
1998        23943       8555 
1999        12860       4904 
2000        36394      14948 
2001        41462      16284 
2002        35034      14992 
2003        57055      23371 
2004        44905      17106 
2005       303402     136709 
2006       330782     147699 
2007       191936      59458 
2008       108086      30833 
2009        88621      24791 
2010       136354      36319 
2011       143360      39010 
2012       170844      37076 
2013       225265      56707 
2014       472480     117252 
2015       711801     186168 
2016       600309     155133 
2017       505535     137457 
2018       301920      85382 
2019       804960     197216 
2020       528268     133890 
2021       711963     166657 
2022       552978     158598 
2023       510718     146319 
2024       550857     158335 
2025       524990     148948 
2026       357112      84085