We present high resolution radio continuum maps of the Galactic nebula Simeis 57 ( = HS 191 = G 80.3+4.7 ) made at the Westerbork Synthesis Radio Telescope and the Dominion Radio Astrophysical Observatory at frequencies of 609 , 1412 and 1420 MHz .
At optical and at radio wavelengths , the nebula has a peculiar “ S ” shape , crossed by long , thin and straight filaments .
The radio maps , combined with other maps from existing databases , show essentially all radio emission from the peculiar and complex nebula to be thermal and optically thin .
Although neither the distance nor the source of excitation of Simeis 57 are known , the nebula can only have a moderate electron density of typically n _ { e } = 100 { cm ^ { -3 } } .
Its mass is also low , not exceeding some tens of solar masses .
Peak emission measures are 5000 pc cm ^ { -6 } .Obscuring dust is closely associated with the nebula , but seems to occur mostly in front of it .
Extinctions vary from A _ { V } = 1.0 mag to A _ { V } = 2.8 mag with a mean of about 2 mag .
The extinction and the far-infrared emission at \lambda 100 \mu m are well-correlated .