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          532        200 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4425       1527 
1996         3602       1265 
1997         2340        798 
1998        23328       9834 
1999        14613       5607 
2000        40704      16903 
2001        41760      16290 
2002        32915      14701 
2003        61902      25658 
2004        48619      18657 
2005        86894      26691 
2006       112592      35934 
2007       207551      63535 
2008       128414      36495 
2009       104429      29323 
2010       121357      33663 
2011       182896      50562 
2012       169609      46919 
2013       264432      74986 
2014       657805     167690 
2015       771712     204317 
2016       578332     154221 
2017       594451     158873 
2018       407026     114169 
2019       930836     227324 
2020       712146     182807 
2021       924166     222255 
2022       691143     197614 
2023       625296     179907 
2024       102420      29649