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          737        299 
1993         1288        480 
1994         1655        608 
1995         2973       1039 
1996         2953       1044 
1997         1815        629 
1998        21571       9179 
1999        13085       5036 
2000        38328      15839 
2001        39193      15219 
2002        30707      13749 
2003        57304      23857 
2004        45980      17651 
2005        80681      24855 
2006       104072      33438 
2007       190393      58911 
2008       110520      31683 
2009        91840      25902 
2010       143715      38632 
2011       155116      43057 
2012       146755      40690 
2013       218236      62212 
2014       560804     142937 
2015       799328     210274 
2016       656201     170503 
2017       550755     149080 
2018       347331      97603 
2019       859191     209693 
2020       610365     155250 
2021       821036     194836 
2022       615201     176108 
2023       554435     158625 
2024       609499     175609 
2025       328019      93868