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         1755        643 
1995         3321       1155 
1996         3535       1242 
1997         2300        785 
1998        23156       9767 
1999        13533       5235 
2000        40110      16634 
2001        40945      15957 
2002        32077      14349 
2003        60196      24990 
2004        47507      18223 
2005        83581      25712 
2006       107953      34571 
2007       198530      61095 
2008       119939      34206 
2009        98446      27703 
2010       113577      31619 
2011       168375      46620 
2012       158415      43852 
2013       236575      67284 
2014       579784     148915 
2015       701167     185933 
2016       676743     175642 
2017       576283     155693 
2018       374102     104955 
2019       900327     220153 
2020       651195     166074 
2021       869267     207260 
2022       644350     184480 
2023       591874     169355 
2024       430073     125236