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          489        185 
1992          767        309 
1993         1356        504 
1994         1746        640 
1995         3285       1143 
1996         3093       1092 
1997         2288        782 
1998        23072       9734 
1999        14410       5524 
2000        39953      16564 
2001        40700      15855 
2002        31950      14287 
2003        59636      24777 
2004        47243      18126 
2005        82907      25507 
2006       106905      34265 
2007       195804      60364 
2008       117508      33543 
2009        96904      27281 
2010       111466      31073 
2011       164881      45687 
2012       156052      43216 
2013       229859      65429 
2014       554966     142231 
2015       715817     188724 
2016       661633     171654 
2017       569094     153744 
2018       365891     102691 
2019       887867     216846 
2020       639595     163002 
2021       860120     204851 
2022       638439     182739 
2023       577753     165397 
2024       563231     162586