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          512        193 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4122       1424 
1996         3581       1258 
1997         2331        795 
1998        23296       9821 
1999        14569       5588 
2000        40581      16845 
2001        41584      16215 
2002        32669      14604 
2003        61612      25534 
2004        48364      18553 
2005        86214      26494 
2006       111696      35670 
2007       205911      63087 
2008       126862      36080 
2009       103334      29025 
2010       119892      33273 
2011       180201      49827 
2012       167352      46305 
2013       259390      73637 
2014       645246     164559 
2015       749364     198883 
2016       575943     153731 
2017       612163     163817 
2018       406412     113885 
2019       931287     227166 
2020       697198     179000 
2021       905982     217239 
2022       676058     193398 
2023       614265     176822 
2024       156091      44683