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         2333        842 
1995         4427       1528 
1996         3602       1265 
1997         2340        798 
1998        23334       9837 
1999        14618       5609 
2000        40729      16914 
2001        41798      16305 
2002        32945      14714 
2003        61987      25693 
2004        48677      18678 
2005        87025      26728 
2006       112716      35968 
2007       207752      63589 
2008       128664      36562 
2009       104589      29366 
2010       121574      33722 
2011       183172      50638 
2012       169824      46978 
2013       264920      75122 
2014       660925     168519 
2015       773127     204837 
2016       577700     154235 
2017       587914     157654 
2018       406721     114102 
2019       927737     226473 
2020       712720     182938 
2021       924991     222483 
2022       692312     197931 
2023       628534     180872 
2024        97865      28544