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          465        177 
1992          727        295 
1993         1283        478 
1994         1640        603 
1995         2918       1020 
1996         2913       1030 
1997         1796        622 
1998        21484       9141 
1999        12944       4986 
2000        38119      15749 
2001        40109      15515 
2002        32080      14188 
2003        56668      23613 
2004        45534      17492 
2005        80181      24706 
2006       103235      33191 
2007       188518      58410 
2008       107853      30970 
2009        90256      25477 
2010       142139      38223 
2011       152179      42258 
2012       143449      39792 
2013       216083      61617 
2014       551763     140508 
2015       792277     208388 
2016       648832     168507 
2017       545773     147720 
2018       341049      95864 
2019       851505     207713 
2020       598025     151867 
2021       808534     191489 
2022       610088     174660 
2023       550335     157495 
2024       609243     174974 
2025       476794     135806