I have an idea how to measure the ecliptic longitude with a sundial type device. Ecliptic longitude is a astronomical variable so I chose this forum. Suppose we have a verticle flag pole poised on the equator of the Earth. A "coordinate circle" is drawn that surrounds the flag pole, radius = ( flag pole height )*tan( e ), e = 23.4393° = tilt of Earth. So when the shadow point crosses the coordinate circle, the altitude of the Sun is 66.5607°. Now with some doodling, I have a conjecture to offer. When the shadow point crosses the coordinate circle, the ecliptic longitude will equal the azimuth of the Sun measured from due east as 0° and positve going counter-clockwise. Take care to note that due east azimuth for the Sun is due west for the shadow point. It is obvious that the shadow point usually crosses the circle twice in a day, so it is assumed that the observer knows to use the reading closest to 24 hours from the previous one. Is this correct? Is what that is being measured the ecliptic longitude?