Reference Frames for Stellar Aberration

There is some confusion in the literature as to what velocity should appear in the stellar aberration formula. Because the aberration formula is usually derived from the same equations as the Doppler shift, where the relative velocity between source and detector is the relevant one, it is often assumed the same holds for aberration. This is not the case. Authors who choose the orbital velocity of the Earth are approximately correct, but they do not always justify the choice. We attempt to sort out the matter with natural reference frames that emphasize the observer's point of view. A multi-dimensional approach is also stressed. This leads to a description that is simple to visualize and one that shows why the Earth's orbital velocity is to a high approximation the correct velocity to use.