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          471        179 
1992          746        302 
1993         1308        487 
1994         1686        619 
1995         3099       1081 
1996         2986       1055 
1997         1890        652 
1998        22325       9434 
1999        13593       5216 
2000        38775      16036 
2001        39564      15372 
2002        30972      13875 
2003        58052      24150 
2004        46601      17880 
2005        81948      25219 
2006       105570      33873 
2007       192878      59576 
2008       114371      32704 
2009        94353      26584 
2010       116019      32119 
2011       160461      44490 
2012       151786      42053 
2013       224353      63905 
2014       568572     144869 
2015       799756     209446 
2016       666178     172810 
2017       558577     151047 
2018       356117     100021 
2019       872109     212918 
2020       624973     159117 
2021       843553     200611 
2022       629050     180048 
2023       564936     161572 
2024       631500     181811 
2025       165643      47164