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Message: <blockquote data-quote="a33" data-source="post: 1050340" data-attributes="member: 332642">I've thought a bit more about this perfect or imperfect tracking of the arc.For any point on earth (between 0 and 81 degrees latitude), the arc has the shape of an ellips (when you're looking at it with axis parallel to the earth axis).However, if you set the axis of your motor rotation in the right angle to the plane of the clarke belt, the rotation 'circle' can be made to follow that ellips again.So mathemathically I think the Huevos method is sound and 'perfect'.I don't think anymore that compromises are needed, in the calculation of modified motor settings.If compromises are needed, I think that would be because in practice the Clarke Belt may not be a perfect circle around the center of the earth, due to gravity anomalies and so; or because an improper way of calculating is used.I came to these conclusions based on another example of an ellips being perfectly tracked as a circle: an offset dish.If you take the line Focal point to G-spot as 'rotation axis', the elliptical rim of the dish is seen as a perfect circle by an LNB feedhorn.I was puzzled for a while that the program Parabola calculator 2.0 uses different feed illumination angles for the horizontal and vertical, as if there would be a kind of anomaly there. There isn't; there only is one illumination angle (and corresponding f/D-ratio-equivalent).The trick is that you have to use the width of the dish where the Focal-Point-to-G-spot line crosses the face of the dish for the horizontal width of the dish, and calculate the LNB-illumination angle from there. Though this might feel contra-intuitive, the 'real' (maximum) width of the dish is not really relevant for that.(So Parabola2 not only calculates wrong focal point for a normal offset dish, alas, it also gives misleading info about illumination angle. <img src="https://www.satellites.co.uk/styles/default/xenforo/smilies/sad.png"  class="smilie" loading="lazy" alt=":(" title="Sad    :(" data-shortname=":(" /> )So also on the Clarke Belt arc, the widest point of the small axis of the 'ellips' (somewhere about +90 and -90 degrees from where you are) is not really important for the calculation. The north/south ends of the ellips at 0 and 180 degrees (as the hight of a dish, in the calculation of illumination angle of offset dish) are more important as starting points for the angle calculations. <img src="https://www.satellites.co.uk/styles/default/xenforo/smilies/smile.png"  class="smilie" loading="lazy" alt=":)" title="Smile    :)" data-shortname=":)" />It has been really interesting, to discover this all!Greetz,A33</blockquote>

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