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         3084       1089 
1997         2288        782 
1998        23066       9732 
1999        14407       5523 
2000        39951      16563 
2001        40693      15852 
2002        31942      14283 
2003        59620      24771 
2004        47231      18122 
2005        82886      25500 
2006       106854      34250 
2007       195665      60328 
2008       117392      33511 
2009        96815      27256 
2010       111403      31057 
2011       164771      45657 
2012       155945      43186 
2013       229669      65376 
2014       554485     142116 
2015       715336     188596 
2016       661414     171595 
2017       568553     153646 
2018       365435     102576 
2019       887496     216738 
2020       639199     162895 
2021       859547     204713 
2022       638200     182678 
2023       578834     165756 
2024       593571     171043