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          503        190 
1992          936        367 
1993         1666        609 
1994         2326        839 
1995         3548       1232 
1996         3576       1256 
1997         2329        794 
1998        23260       9807 
1999        14526       5570 
2000        40476      16796 
2001        43059      16697 
2002        32496      14526 
2003        61254      25394 
2004        47991      18405 
2005        85468      26276 
2006       110920      35442 
2007       204187      62615 
2008       125348      35672 
2009       101973      28654 
2010       118473      32905 
2011       177762      49160 
2012       165141      45633 
2013       256159      72453 
2014       638528     162469 
2015       741820     196282 
2016       570397     152154 
2017       605752     162886 
2018       397912     111315 
2019       939128     229887 
2020       689190     176658 
2021       896129     214536 
2022       665072     190228 
2023       604325     174005 
2024       212959      61522