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Re: ATM Change of Plans, F/2 -> F/3.2


>Isn't coma...

For a parboloidal mirror, third order abberation theory yields

  spherical abberation   beta = 0.0
  sagittal coma          beta = theta / (16 * focal_ratio^2)
  astigmatism            beta = (L + f)^2 * theta^2 / (2 * f^2 * focal_ratio)

where
  beta    angular diameter of blur spot in radians
  theta   half field angle in radians
  L       distance from mirror to aperture stop
  f       focal length

Source:  Handbook of Optics



Anthony