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         4020       1390 
1996         3581       1258 
1997         2331        795 
1998        23285       9817 
1999        14561       5585 
2000        40569      16839 
2001        41564      16208 
2002        32661      14601 
2003        61585      25523 
2004        48325      18537 
2005        86182      26484 
2006       111627      35649 
2007       205734      63039 
2008       126739      36047 
2009       103242      28999 
2010       119807      33250 
2011       180002      49773 
2012       167113      46242 
2013       259072      73551 
2014       644493     164377 
2015       748898     198757 
2016       575281     153543 
2017       613219     164042 
2018       406226     113838 
2019       933840     227878 
2020       696780     178885 
2021       905511     217090 
2022       674425     192929 
2023       613377     176574 
2024       159747      45783