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          532        200 
1992          936        367 
1993         1678        613 
1994         2342        845 
1995         4445       1534 
1996         3605       1266 
1997         2340        798 
1998        23370       9850 
1999        14660       5625 
2000        40959      17012 
2001        42075      16425 
2002        33383      14897 
2003        62512      25905 
2004        49174      18874 
2005        88099      27037 
2006       114115      36384 
2007       209443      64053 
2008       130886      37164 
2009       106548      29896 
2010       123601      34253 
2011       186991      51670 
2012       172880      47810 
2013       270315      76606 
2014       670450     170989 
2015       783581     207642 
2016       571111     153135 
2017       530446     147784 
2018       411948     115655 
2019       917972     224273 
2020       725057     186207 
2021       933184     224590 
2022       700146     200288 
2023       662861     190696