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         1669        610 
1994         2326        839 
1995         3706       1284 
1996         3578       1257 
1997         2335        796 
1998        23272       9812 
1999        14535       5574 
2000        40496      16805 
2001        43081      16706 
2002        32546      14549 
2003        61325      25422 
2004        48049      18429 
2005        85629      26324 
2006       111060      35483 
2007       204628      62735 
2008       125762      35782 
2009       102328      28752 
2010       118899      33015 
2011       178383      49331 
2012       166111      45844 
2013       258517      72895 
2014       643617     163310 
2015       744196     196893 
2016       572261     152657 
2017       610132     163612 
2018       403869     112681 
2019       942276     230685 
2020       691617     177345 
2021       898617     215209 
2022       667310     190883 
2023       606585     174646 
2024       199116      57281