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         2339        844 
1995         4439       1532 
1996         3605       1266 
1997         2337        797 
1998        23368       9849 
1999        14654       5623 
2000        40911      16992 
2001        42017      16400 
2002        33303      14861 
2003        62446      25879 
2004        49082      18837 
2005        87911      26981 
2006       113850      36306 
2007       209186      63983 
2008       130552      37074 
2009       106243      29814 
2010       123110      34125 
2011       186263      51476 
2012       172219      47630 
2013       269414      76366 
2014       669119     170641 
2015       782015     207226 
2016       573371     153681 
2017       533700     148365 
2018       411093     115402 
2019       921524     225188 
2020       723596     185814 
2021       931555     224233 
2022       697390     199497 
2023       651132     187325 
2024            4          0