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         2985       1043 
1996         2953       1044 
1997         1819        630 
1998        21582       9184 
1999        13124       5049 
2000        38395      15869 
2001        39230      15236 
2002        30757      13771 
2003        57412      23900 
2004        46072      17686 
2005        80771      24883 
2006       104220      33483 
2007       190705      58996 
2008       111025      31819 
2009        92064      25964 
2010       144182      38751 
2011       155822      43250 
2012       147297      40835 
2013       218812      62374 
2014       562419     143339 
2015       799362     210239 
2016       656095     170461 
2017       551759     149388 
2018       348794      98012 
2019       860582     210077 
2020       612846     155951 
2021       824002     195589 
2022       616420     176456 
2023       555574     158946 
2024       611934     176291 
2025       286079      82330