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          538        202 
1992          936        367 
1993         1690        617 
1994         2360        851 
1995         4502       1553 
1996         3614       1269 
1997         2368        807 
1998        23431       9872 
1999        14735       5656 
2000        41242      17139 
2001        42378      16546 
2002        33665      15023 
2003        62997      26104 
2004        49610      19040 
2005        89208      27367 
2006       115771      36854 
2007       211500      64605 
2008       132914      37710 
2009       108584      30443 
2010       126188      34953 
2011       189685      52434 
2012       177125      48967 
2013       274219      77682 
2014       677098     172758 
2015       775765     206081 
2016       553724     149070 
2017       476060     135988 
2018       408897     114884 
2019       811230     198562 
2020       722690     185670 
2021       939579     226114 
2022       828610     227637 
2023       552796     157755