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          740        300 
1993         1296        483 
1994         1658        609 
1995         2982       1042 
1996         2953       1044 
1997         1819        630 
1998        21580       9183 
1999        13100       5041 
2000        38378      15861 
2001        39219      15231 
2002        30748      13767 
2003        57380      23888 
2004        46046      17676 
2005        80729      24870 
2006       104172      33467 
2007       190601      58968 
2008       110913      31789 
2009        92021      25952 
2010       144060      38720 
2011       155581      43184 
2012       147162      40799 
2013       218586      62312 
2014       561742     143173 
2015       799237     210227 
2016       656065     170461 
2017       551245     149240 
2018       348218      97851 
2019       860069     209950 
2020       612043     155724 
2021       823105     195381 
2022       616025     176343 
2023       555119     158815 
2024       610773     175973 
2025       294893      84963