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         2329        840 
1995         3808       1319 
1996         3578       1257 
1997         2335        796 
1998        23277       9814 
1999        14545       5578 
2000        40526      16819 
2001        43135      16731 
2002        32600      14574 
2003        61444      25470 
2004        48196      18485 
2005        85924      26406 
2006       111371      35573 
2007       205203      62888 
2008       126301      35928 
2009       102826      28885 
2010       119375      33139 
2011       179189      49552 
2012       166411      46048 
2013       257542      73133 
2014       641543     163561 
2015       745198     197741 
2016       573346     153002 
2017       612108     164077 
2018       404774     113463 
2019       940489     229900 
2020       695145     178305 
2021       902251     216133 
2022       669680     191530 
2023       610877     175859 
2024       197200      56682