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         1501        553 
1994         2317        836 
1995         3365       1170 
1996         3576       1256 
1997         2326        793 
1998        23250       9803 
1999        14520       5567 
2000        40436      16778 
2001        42993      16672 
2002        32451      14505 
2003        61101      25334 
2004        47903      18372 
2005        85125      26173 
2006       110573      35336 
2007       203487      62425 
2008       124715      35503 
2009       101298      28473 
2010       117886      32750 
2011       176546      48823 
2012       164017      45353 
2013       254163      71892 
2014       604225     154703 
2015       729324     193407 
2016       713367     184315 
2017       600483     162000 
2018       395451     110810 
2019       928506     227938 
2020       683258     175019 
2021       892652     213652 
2022       662739     189554 
2023       601526     173196 
2024       241875      70014