Correcting the astronomy

The astronomy angles within the pyramid are correct and therefore the dynamic geometry that is forming them also needs to be astronomically correct. The interactive drawing shows the dynamic Sun plot that was seen on a previous page (page E5) with the Sun carving out the 'vertical' trial passage shaft at the bottom right of the screen by using the gallery roof test angle to form the second Sun line.

If you zoom in on the gallery area where the key is being projected onto the gallery floor you can see that there is a problem. The two ends of the yellow part of the plot line represent Perihelion and Aphelion but the projection plot is continuing up the gallery and drawing out the blue section of the plot, which is an undefined area.

The blue section of the plot needs to be removed, and at the same time the integrity of the astronomy needs to be preserved : as the Earth moves along the yellow part of the plot, it needs to do so only once per year. The way to achieve this is to put a gearing ratio into the rotation of the secondary ellipse so that the lower northern shaft line oscillates at exactly half the frequency of the rotation of the principal ellipse.

This gearing is applied to the dynamic geometry on the next page.