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          770        310 
1993         1359        505 
1994         2298        829 
1995         3365       1170 
1996         3576       1256 
1997         2326        793 
1998        23240       9799 
1999        14517       5566 
2000        40428      16774 
2001        42986      16669 
2002        32431      14496 
2003        61070      25323 
2004        47872      18363 
2005        85066      26155 
2006       110502      35313 
2007       203383      62398 
2008       124615      35475 
2009       101148      28432 
2010       117776      32721 
2011       176320      48762 
2012       163921      45327 
2013       253687      71763 
2014       603822     154599 
2015       728803     193267 
2016       717597     185285 
2017       600181     161969 
2018       395190     110736 
2019       929818     228312 
2020       682627     174834 
2021       892126     213499 
2022       662531     189488 
2023       600939     173029 
2024       255483      74020