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Thanks Fred. I share your concern, especially for the extremely faint Sharpless 308 images. At first I thought that the diffuse halo of OIII (with a little H alpha) emission surrounding the inner bubble was an artefact caused by light pollution. No doubt the background emissions are not entirely faithful because of light pollution gradients. However, with each passing night I began to think that at least some of the features in the background emissions were real. The dark halo surrounding the bright inner bubble may be the void blown out by an earlier, more ancient episode of intense stellar wind. Next I plan to do some more OIII runs using a focal reducer to increase the field of view. The idea is to see if the OIII emission near the edge of the field is part of a diffuse secondary bubble, or just a combination of light pollution gradients combined with diffuse OIII emission permeating the region.
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