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         4425       1527 
1996         3593       1262 
1997         2337        797 
1998        23319       9830 
1999        14596       5600 
2000        40663      16884 
2001        41688      16260 
2002        32833      14669 
2003        61778      25605 
2004        48535      18621 
2005        86670      26624 
2006       112208      35822 
2007       206919      63364 
2008       127772      36322 
2009       104029      29212 
2010       120776      33510 
2011       181947      50306 
2012       168837      46709 
2013       262771      74515 
2014       653843     166716 
2015       760946     201819 
2016       579410     154530 
2017       606612     161924 
2018       406900     114052 
2019       932689     227435 
2020       707504     181575 
2021       921027     221467 
2022       688513     196869 
2023       620013     178429 
2024       133235      38189