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         2948       1030 
1996         2941       1040 
1997         1813        628 
1998        21554       9171 
1999        13067       5029 
2000        38241      15802 
2001        39145      15200 
2002        30585      13703 
2003        57157      23800 
2004        45843      17601 
2005        80549      24814 
2006       103872      33379 
2007       189975      58799 
2008       109926      31524 
2009        91464      25801 
2010       143255      38515 
2011       154377      42853 
2012       145754      40417 
2013       217627      62043 
2014       558300     142263 
2015       797683     209814 
2016       654585     170058 
2017       549525     148749 
2018       345626      97136 
2019       857984     209363 
2020       607244     154418 
2021       817041     193831 
2022       613628     175664 
2023       553392     158343 
2024       608029     175068 
2025       363080     104446