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        40903      16989 
2001        42015      16399 
2002        33293      14856 
2003        62430      25873 
2004        49064      18830 
2005        87884      26973 
2006       113792      36289 
2007       209124      63965 
2008       130494      37059 
2009       106110      29779 
2010       123019      34101 
2011       186161      51447 
2012       172048      47583 
2013       269254      76321 
2014       668785     170557 
2015       781614     207125 
2016       573208     153639 
2017       535845     148760 
2018       411044     115378 
2019       923399     225659 
2020       723351     185745 
2021       931245     224154 
2022       697119     199413 
2023       649005     186716