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        13064       5028 
2000        38235      15800 
2001        39145      15200 
2002        30574      13699 
2003        57150      23797 
2004        45835      17598 
2005        80538      24811 
2006       103866      33377 
2007       189962      58795 
2008       109922      31523 
2009        91465      25801 
2010       143234      38509 
2011       154347      42845 
2012       145747      40415 
2013       217591      62032 
2014       558224     142241 
2015       797627     209796 
2016       654534     170045 
2017       549482     148737 
2018       345569      97119 
2019       857902     209340 
2020       607162     154393 
2021       816981     193815 
2022       613518     175632 
2023       553378     158354 
2024       607974     175053 
2025       362719     104358