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          492        186 
1992          767        309 
1993         1356        504 
1994         1752        642 
1995         3312       1152 
1996         3344       1176 
1997         2291        783 
1998        23125       9755 
1999        14439       5535 
2000        40034      16601 
2001        40883      15928 
2002        32121      14354 
2003        59998      24916 
2004        47381      18179 
2005        83275      25620 
2006       107510      34440 
2007       197508      60820 
2008       119002      33949 
2009        97862      27543 
2010       112788      31412 
2011       167039      46262 
2012       157620      43641 
2013       234005      66576 
2014       577492     147304 
2015       759526     198606 
2016       672925     174221 
2017       574006     155049 
2018       371188     104155 
2019       895780     218949 
2020       647271     165071 
2021       866463     206542 
2022       642110     183838 
2023       586365     167735 
2024       490530     141835