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         3571       1239 
1996         3576       1256 
1997         2329        794 
1998        23265       9809 
1999        14531       5572 
2000        40484      16800 
2001        43077      16704 
2002        32533      14543 
2003        61302      25413 
2004        48037      18424 
2005        85576      26308 
2006       110988      35462 
2007       204480      62695 
2008       125588      35737 
2009       102173      28711 
2010       118723      32970 
2011       178159      49270 
2012       165358      45743 
2013       255728      72533 
2014       640542     162848 
2015       743644     196711 
2016       571644     152472 
2017       608499     163310 
2018       406900     112740 
2019       941034     230372 
2020       690633     177073 
2021       897668     214936 
2022       666621     190683 
2023       605736     174402 
2024       206472      59476