W1, W3, and W4 images of BM Cas. Each image subtends 600″ on a side, with north at the top and east to the left. The W2 image is not shown as it is similar to the W1 image. BM Cas is one of the brightest sources in the W3 and W4 images. The bright source in the lower left-hand corner of the W3 and W4 images is GAIA 524180215659014912, which has a parallax of 0﹩\mathop{.}\limits^{\unicode{x02033}}﹩113, and so is in the background. The images have angular resolutions that range from ∼11″ FWHM in W1 to 21″ FWHM in W4. BM Cas is an isolated, luminous MIR source. IR emission from the shell detected in the Fe II lines (Section 5) is not resolved.