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          532        200 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4425       1527 
1996         3602       1265 
1997         2340        798 
1998        23330       9835 
1999        14615       5608 
2000        40719      16910 
2001        41779      16297 
2002        32925      14706 
2003        61934      25670 
2004        48635      18663 
2005        86944      26705 
2006       112620      35942 
2007       207572      63541 
2008       128471      36510 
2009       104478      29336 
2010       121396      33674 
2011       182953      50578 
2012       169667      46934 
2013       264558      75021 
2014       659807     168192 
2015       772216     204545 
2016       578100     154231 
2017       590076     157915 
2018       406547     114055 
2019       929992     227002 
2020       712123     182781 
2021       924366     222312 
2022       691373     197674 
2023       625489     179996 
2024       102531      29679