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          492        186 
1992          767        309 
1993         1356        504 
1994         1746        640 
1995         3291       1145 
1996         3261       1148 
1997         2288        782 
1998        23093       9743 
1999        14418       5527 
2000        39977      16575 
2001        40802      15894 
2002        32318      14413 
2003        59816      24845 
2004        47317      18155 
2005        83072      25559 
2006       107121      34327 
2007       196452      60536 
2008       118068      33695 
2009        97340      27402 
2010       111931      31192 
2011       165673      45901 
2012       156653      43378 
2013       231358      65850 
2014       575282     146725 
2015       751006     196497 
2016       669980     173475 
2017       571337     154325 
2018       367966     103257 
2019       890810     217607 
2020       643187     163960 
2021       863124     205629 
2022       640012     183191 
2023       580064     166059 
2024       513167     148340