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         4263       1472 
1996         3584       1259 
1997         2334        796 
1998        23301       9823 
1999        14577       5592 
2000        40624      16865 
2001        41635      16236 
2002        32740      14634 
2003        61668      25558 
2004        48443      18585 
2005        86438      26556 
2006       111950      35745 
2007       206377      63216 
2008       127333      36205 
2009       103642      29106 
2010       120244      33368 
2011       181013      50048 
2012       168081      46504 
2013       260950      74016 
2014       646675     164954 
2015       751819     199545 
2016       577139     154057 
2017       611250     163455 
2018       407675     114229 
2019       931781     227251 
2020       700577     179915 
2021       928773     222310 
2022       678433     194059 
2023       616062     177325 
2024       148766      42638