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         3518       1222 
1996         3576       1256 
1997         2329        794 
1998        23260       9807 
1999        14524       5569 
2000        40476      16796 
2001        43052      16694 
2002        32496      14526 
2003        61241      25388 
2004        47980      18401 
2005        85408      26259 
2006       110874      35428 
2007       204087      62587 
2008       125235      35642 
2009       101901      28635 
2010       118370      32878 
2011       177646      49128 
2012       164985      45593 
2013       255910      72384 
2014       641512     162577 
2015       741628     196159 
2016       570042     152060 
2017       604965     162731 
2018       397589     111227 
2019       938422     229732 
2020       688691     176517 
2021       895626     214419 
2022       664881     190174 
2023       604019     173917 
2024       212938      61524