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          503        190 
1992          936        367 
1993         1666        609 
1994         2326        839 
1995         3446       1198 
1996         3576       1256 
1997         2329        794 
1998        23263       9808 
1999        14524       5569 
2000        40476      16796 
2001        43050      16693 
2002        32489      14523 
2003        61226      25381 
2004        47977      18400 
2005        85395      26255 
2006       110848      35420 
2007       204046      62576 
2008       125200      35633 
2009       101841      28618 
2010       118333      32868 
2011       177569      49107 
2012       164931      45578 
2013       255840      72363 
2014       635251     161269 
2015       742651     196196 
2016       570361     152071 
2017       603341     162565 
2018       397399     111173 
2019       938129     229655 
2020       687931     176302 
2021       895293     214323 
2022       664636     190104 
2023       603766     173846 
2024       217206      62683