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         4172       1441 
1996         3584       1259 
1997         2334        796 
1998        23296       9821 
1999        14573       5590 
2000        40612      16859 
2001        41621      16231 
2002        32707      14620 
2003        61653      25552 
2004        48400      18568 
2005        86320      26524 
2006       111839      35713 
2007       206158      63154 
2008       127102      36144 
2009       103497      29069 
2010       120094      33328 
2011       180598      49934 
2012       167743      46413 
2013       260241      73815 
2014       646014     164768 
2015       750281     199137 
2016       576580     153904 
2017       611332     163609 
2018       407367     114146 
2019       931223     227134 
2020       698760     179405 
2021       907779     217738 
2022       677539     193819 
2023       615226     177086 
2024       150570      43067