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          512        193 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4204       1452 
1996         3584       1259 
1997         2334        796 
1998        23298       9822 
1999        14575       5591 
2000        40622      16864 
2001        41635      16236 
2002        32736      14632 
2003        61665      25557 
2004        48427      18578 
2005        86401      26546 
2006       111921      35737 
2007       206334      63204 
2008       127264      36188 
2009       103607      29097 
2010       120198      33355 
2011       180886      50012 
2012       167996      46482 
2013       260748      73959 
2014       646543     164916 
2015       751024     199339 
2016       577118     154054 
2017       611964     163681 
2018       407789     114257 
2019       931581     227212 
2020       700124     179784 
2021       928467     222218 
2022       678174     193988 
2023       615907     177282 
2024       150362      43050