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Old 19-04-2019, 10:36 PM
Saturnine (Jeff)
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Join Date: Jul 2008
Location: Wollongong
Posts: 2,134
Great images once again, has been fun following Ar 2738 on its journey around Sol.
I need to brush up on my solar terminologies but I presume that the Wilson Affect that you mention is caused by the cooler sunspots being depressed into the photosphere, so that when close to the limb the leading edge of the penumbra is tilted slightly more to our line of sight thus appearing wider. Assuming that the spot has a reasonably symmetrical shape.
It would seem that the spot is an oval shape now with the long axis pointing to our line of sight, which may explain why the trailing side of the penumbra looks wider.
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