Abell 12 is called "The Hidden Nebula": at 7000 light years away, it is almost drowned out by the 4th magnitude star system Mu Orionis (actually a spectroscopic quadruple system), which is only 150 light years from us. In angular size Abell 12 is only 37 arc-sec across, so very difficult to pick up any detail.
The nebula is a hard
x-ray source likely due to a shocked wave-front at a temperature of a million Kelvin(!),generated by fast interstellar winds from the central star; and not soft x-rays which would come from the central star itself.
Using my new LeNhance dual-band (Hapha,OIII) filter for the first time really helped me to reduced the intense glare of Mu,and providing much better contrast in the nebula, especially given my bright city skies.
One might not have expected to see diffraction spikes on Mu, given the optics are a Celestron SCT: apparently this is likely due to inhomogeneities in the glass of the corrector plate, an artifact of how the glass was cast. None of the artifacts around Mu are due to the LeNhance filter, they were just as evident in some trial shots I did without a filter.
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