From the geocentrist, I need an explanation. My physics book also used aberration to establish the speed of light. For their formular they used an established figure 30,557 meters per second for the caculated orbital speed of the earth around the sun. Taking the triangle I used before, with the angle of aberation of 20.45" and making the base line equal to the velocity of the earth, 30,557 meters per second ,and the vertical line equal to the speed of light, using -- Tan 20.45 = 30557over V of light squared. .or .0001003 Working back from the Tan tables this gave a fairly accurate 3.047 X 10/8th meters per second. If the earth is not moving, how do we account for the figures working out? Is it because they made the assumption that the base line measurement was due to earth movement rather than star movement. Yet for this to be so, it must involve a rather complex star/cosmos movement forward and backward annually in addition to the daily revolution, and the annual wobbling plate for the seasons. Seems like a lot of complexity, just to con someone into thinking that we rotated and revolved around the sun. Sorry if this has been gone over before I came on the scene. Philip.