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         1749        641 
1995         3294       1146 
1996         3279       1154 
1997         2291        783 
1998        23100       9746 
1999        14426       5530 
2000        39995      16583 
2001        40834      15907 
2002        32069      14332 
2003        59893      24873 
2004        47327      18159 
2005        83123      25575 
2006       107197      34349 
2007       196719      60607 
2008       118318      33762 
2009        97474      27438 
2010       112137      31243 
2011       165997      45988 
2012       156843      43431 
2013       231916      66008 
2014       575758     146848 
2015       752422     196858 
2016       670629     173640 
2017       571902     154481 
2018       368731     103471 
2019       891803     217880 
2020       644034     164197 
2021       863937     205858 
2022       640463     183365 
2023       584449     167274 
2024       511525     147857