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         2234        807 
1995         3359       1168 
1996         3570       1254 
1997         2326        793 
1998        23228       9795 
1999        14500       5560 
2000        40381      16754 
2001        42882      16627 
2002        32398      14482 
2003        60906      25261 
2004        47783      18329 
2005        84599      26018 
2006       109776      35100 
2007       202170      62067 
2008       123361      35130 
2009       100167      28170 
2010       116568      32406 
2011       173883      48109 
2012       161602      44723 
2013       247248      70183 
2014       589862     151490 
2015       719935     191070 
2016       707760     183158 
2017       597183     161272 
2018       392310     109942 
2019       926056     227406 
2020       676742     173286 
2021       888877     212592 
2022       660555     188914 
2023       612685     173621 
2024       269452      78114