Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          468        178 
1992          735        298 
1993         1283        478 
1994         1655        608 
1995         2945       1029 
1996         2941       1040 
1997         1810        627 
1998        21554       9171 
1999        13058       5026 
2000        38235      15800 
2001        39145      15200 
2002        30572      13698 
2003        57150      23797 
2004        45835      17598 
2005        80538      24811 
2006       103866      33377 
2007       189962      58795 
2008       109906      31519 
2009        91459      25799 
2010       143230      38508 
2011       154339      42843 
2012       145739      40413 
2013       217587      62031 
2014       558181     142229 
2015       797605     209789 
2016       654517     170040 
2017       549455     148729 
2018       345558      97116 
2019       857865     209330 
2020       607141     154388 
2021       816965     193810 
2022       613512     175630 
2023       553371     158352 
2024       607948     175045 
2025       362652     104345