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         3156       1113 
1997         2288        782 
1998        23078       9736 
1999        14410       5524 
2000        39958      16566 
2001        40709      15859 
2002        31958      14290 
2003        59678      24792 
2004        47260      18134 
2005        82931      25516 
2006       106971      34283 
2007       195973      60408 
2008       117701      33595 
2009        97018      27313 
2010       111624      31114 
2011       165140      45756 
2012       156220      43263 
2013       230337      65561 
2014       555340     142329 
2015       735942     193196 
2016       667583     172899 
2017       569681     153898 
2018       366549     102867 
2019       888561     217042 
2020       640442     163229 
2021       860827     205049 
2022       638756     182833 
2023       577623     165343 
2024       532727     154073