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         4192       1448 
1996         3584       1259 
1997         2334        796 
1998        23296       9821 
1999        14575       5591 
2000        40616      16861 
2001        41633      16235 
2002        32717      14624 
2003        61657      25554 
2004        48408      18571 
2005        86352      26533 
2006       111906      35732 
2007       206265      63183 
2008       127184      36167 
2009       103564      29086 
2010       120163      33346 
2011       180747      49974 
2012       167889      46452 
2013       260504      73891 
2014       646256     164837 
2015       750669     199241 
2016       576893     153992 
2017       611561     163630 
2018       407688     114229 
2019       931541     227210 
2020       699743     179676 
2021       928090     222109 
2022       677921     193915 
2023       615512     177168 
2024       149698      42853