LNB position(Focal Point) on 6ft solid dish

Dear all,
Pls help me, how can i find exact position(Focal Point) for ku band lnb on 6ft solid ku/c band dish. Details of dish mentioned below.

Solid 180cm C/Ku Band Dish Antenna - 6FT
C band gain: 4GHz 32.80dB
Ku band gain @ 12.45GHz 44.26dB
Material steel plate
Finishing polyester powder coating
Support ground mount or polar mount
Color: White/gray
Elevation angle range: 0-90
Azimuth 0 -360
Aperture efficiency: 75%
Not damage 60m/sec
Working environmental temperature -40--+60
Size - 180cm - 6ft
Packing - 6 piece/Box


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