The 12m Telescope Primary Focus Plate Scale
The primary focus plate scale, which determines the amount of beam displacement as a function of lateral displacement of the subreflector, is given by
where is the beam deviation on the sky, F(r) is the receiver feed illumination pattern, and f is the primary focal length. The term in braces is often called the “beam deviation factor”. For the 12m receivers F(r) is given by
For the 12 Meter Telescope, f = D, which means that the beam deviation factor is 0.827 and that:
The plate scale for prime focus subreflector lateral movement = 31.5 ” /mm
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