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A low-contrast web-like pattern most readily seen in hydrogen alpha or Calcium K outlining bundles of magnetic fields that concentrate around the edge of supergranulation cells.
Supergranules are enormous clusters of ordinary granules with a diameter of about 30000km. Fluid motion within the supergranule concentrates magnetic fields at the edges.
Source: Observing the Sun, A Pocket Field Guide. Jamey L Jenkins, Springer.
This is an “inverted” Calcium K image of the Sun on 12th September 2014 taken with a 1000/100mm refractor, Baader B1200 CaK module, Baader K-line filter and Skyris 274m CCD camera.