This is something for astrophotographers (!!!). Perhaps this topic is already mentioned in this forum, somewhere. I'm new here since a couple of days, I really should explore everything which was written in here!

In the book Gepolariseerd Licht in de Natuur (Polarized Light in Nature) by dr. G. P. Konnen (1980) there is a couple of interesting telescopic black-and-white photographs of Messier 1 (the Crab Nebula), seen through a rotating polarizer. Both photographs show remarkable changes in the shape of this nebula. Is it known how many of these nebulae show these remarkable (polarisation-related) changes? Is there a catalogue of this kind of nebulae?
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