SUNSPOT GROUP CLASSIFICATION (Modified Zurich Sunspot Classification)

A - A small single unipolar SUNSPOT or very small group of spots without PENUMBRA. B - Bipolar sunspot group with no penumbra. C - An elongated bipolar sunspot group. One sunspot must have penumbra. D - An elongated bipolar sunspot group with penumbra on both ends of the group. E - An elongated bipolar sunspot group with penumbra on both ends. Longitudinal extent of penumbra exceeds 10 deg. but not 15 deg. F - An elongated bipolar sunspot group with penumbra on both ends. Longitudinal extent of penumbra exceeds 15 deg. H - A unipolar sunspot group with penumbra.

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