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         3264       1149 
1997         2291        783 
1998        23100       9746 
1999        14420       5528 
2000        39982      16577 
2001        40811      15898 
2002        32054      14326 
2003        59840      24854 
2004        47322      18157 
2005        83102      25568 
2006       107182      34345 
2007       196601      60576 
2008       118243      33741 
2009        97437      27428 
2010       112044      31221 
2011       165876      45956 
2012       156779      43413 
2013       231753      65961 
2014       575593     146804 
2015       751846     196714 
2016       670443     173593 
2017       571767     154443 
2018       368471     103399 
2019       891493     217791 
2020       643749     164118 
2021       863755     205806 
2022       640300     183317 
2023       580092     166058 
2024       511351     147809