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         1669        610 
1994         2326        839 
1995         3790       1313 
1996         3578       1257 
1997         2335        796 
1998        23274       9813 
1999        14540       5576 
2000        40506      16809 
2001        43097      16713 
2002        32575      14563 
2003        61371      25441 
2004        48102      18451 
2005        85739      26356 
2006       111172      35515 
2007       204912      62810 
2008       125978      35840 
2009       102530      28806 
2010       119069      33058 
2011       178751      49431 
2012       166281      45920 
2013       258123      72961 
2014       643091     163383 
2015       746384     197403 
2016       574095     153070 
2017       611715     163891 
2018       408354     113669 
2019       943154     230840 
2020       693262     177789 
2021       900218     215604 
2022       668249     191131 
2023       608636     175223 
2024       200192      57600