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And if that were not enough, my Takahashi Mewlon 180 Cassegrainian is a Dall-Kirkham design!
From Wiki:
"It (DK) uses a concave elliptical primary mirror and a convex spherical secondary. While this system is easier to grind than a classic Cassegrain or Ritchey-Chretien system, it does not correct for off-axis coma and field curvature so the image degrades quickly off-axis".
Cheers
Dennis
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