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          468        178 
1992          735        298 
1993         1288        480 
1994         1655        608 
1995         2956       1033 
1996         2950       1043 
1997         1813        628 
1998        21566       9177 
1999        13079       5034 
2000        38290      15823 
2001        39177      15212 
2002        30686      13740 
2003        57233      23830 
2004        45916      17627 
2005        80610      24832 
2006       103953      33403 
2007       190231      58868 
2008       110273      31617 
2009        91633      25846 
2010       143525      38582 
2011       154746      42954 
2012       146415      40596 
2013       217931      62128 
2014       559504     142589 
2015       798791     210106 
2016       655383     170276 
2017       550561     148998 
2018       346398      97347 
2019       858767     209566 
2020       608932     154890 
2021       819037     194304 
2022       614429     175893 
2023       553947     158494 
2024       608451     175310 
2025       352120     100718