Recently I noticed some faint blue structures in one of my Samyang 135 images of Sh2-183, but they were too faint for me to be sure they really existed. Moreover, I could not find any images of these possible objects. So a few days ago I took the chance of aiming my dual-RASA8 rig at this area in Cassiopeia. And, there they were. I imaged with my IDAS NBZ dual-band filter, so Ha and Oiii. Thus, these blue structures are likely to be Oiii emitting nebulosity although I cannot be 100 % sure they are not blue reflection nebulosity (there is that bright star nearby). They do look at least partly quite filamentous, which opens for the possibility that they are part of a supernova remnant (SNR). However, when I look in the SNR catalogue (
https://www.mrao.cam.ac.uk/surveys/snrs/snrs.data.html) there is nothing registered in that spot. The closest is Tycho Brahe's SN (
https://www.mrao.cam.ac.uk/surveys/snrs/snrs.G120.1+1.4.html), which is just outside the right edge of my image. But that SNR is as far as I understand it only emitting X-rays (and radio waves), and no visual light.
Any suggestions for what it could be?
The image also shows Oiii filaments around Sh2-181, which are also seen in another of my recent images (
https://www.astrobin.com/1dm109/)
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