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          492        186 
1992          770        310 
1993         1356        504 
1994         2128        771 
1995         3354       1166 
1996         3567       1253 
1997         2326        793 
1998        23203       9784 
1999        14493       5557 
2000        40344      16737 
2001        41284      16090 
2002        32333      14457 
2003        60752      25204 
2004        47688      18291 
2005        84219      25906 
2006       109202      34933 
2007       200974      61748 
2008       122337      34851 
2009        99519      27994 
2010       115538      32135 
2011       171845      47557 
2012       160622      44453 
2013       243791      69242 
2014       585376     150367 
2015       709307     188188 
2016       684254     177537 
2017       579744     156808 
2018       381787     107074 
2019       910003     223008 
2020       658706     168320 
2021       874533     208637 
2022       657931     188168 
2023       606026     172429 
2024       291865      84561