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        21574       9180 
1999        13088       5037 
2000        38332      15841 
2001        39200      15222 
2002        30709      13750 
2003        57317      23862 
2004        45986      17653 
2005        80681      24855 
2006       104100      33446 
2007       190434      58923 
2008       110568      31696 
2009        91862      25908 
2010       143749      38640 
2011       155201      43080 
2012       146792      40700 
2013       218294      62228 
2014       560940     142975 
2015       799332     210272 
2016       656227     170508 
2017       550873     149111 
2018       347483      97646 
2019       859400     209752 
2020       610668     155334 
2021       821312     194915 
2022       615321     176144 
2023       554508     158645 
2024       609681     175663 
2025       323134      92437