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          468        178 
1992          732        297 
1993         1283        478 
1994         1655        608 
1995         2942       1028 
1996         2941       1040 
1997         1807        626 
1998        21544       9167 
1999        13042       5020 
2000        38207      15789 
2001        39127      15194 
2002        30560      13692 
2003        57106      23780 
2004        45807      17589 
2005        80511      24804 
2006       103801      33358 
2007       189846      58764 
2008       109608      31438 
2009        91345      25768 
2010       143127      38481 
2011       154080      42772 
2012       145575      40370 
2013       217388      61978 
2014       557468     142033 
2015       797032     209638 
2016       653803     169846 
2017       548948     148589 
2018       345067      96982 
2019       857331     209191 
2020       606252     154136 
2021       815895     193521 
2022       613070     175506 
2023       553039     158257 
2024       607370     174873 
2025       381112     109560