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          770        310 
1993         1356        504 
1994         2252        813 
1995         3362       1169 
1996         3570       1254 
1997         2326        793 
1998        23228       9795 
1999        14503       5561 
2000        40391      16758 
2001        42934      16647 
2002        32402      14484 
2003        60978      25288 
2004        47814      18340 
2005        84772      26069 
2006       110054      35183 
2007       202715      62218 
2008       124043      35320 
2009       100672      28304 
2010       117182      32567 
2011       175176      48452 
2012       163116      45109 
2013       251327      71119 
2014       597079     153016 
2015       723066     191813 
2016       707660     183121 
2017       598083     161416 
2018       392872     110099 
2019       925850     227286 
2020       718357     182805 
2021       890378     213028 
2022       661105     189068 
2023       614502     174000 
2024       269004      77983