Got it in one
However, not everyone would think that. The telling fact in this equation is when you do a Doppler study of the galaxy's rotation. The side with all the dust is blueshift whilst the other "dustless" side is redshifted. The orientation of the galaxy is the thing which throws most people off. It's a difficult little beggar because it's almost edge on and the details you can see in the galaxy's arms tend to throw many people off the scent, so to speak. When you get to see piccies of it upside down relative to your piccie (depending on where in the sky they took the piccie), that makes it even harder to figure out once you tell them they're looking at the galaxy's underside.