Hi Dan,
To me the value of the EQT at the intersection is an indication of the 
asymmetry of the analemma caused by the difference between the solstice and 
perihelion dates. The tilt of the earths axis is one parameter that defines the 
analemma. This is shown at the extremes, the summer and winter solstices. The 
eccentricity of the orbit is the other parameter that defines the analemma. 
This is indicated by the perihelion. If the date of the perihelion is the same 
as the solstice, I would expect the curve would be symmetrical and the EQT at 
the intersection would be equal to zero. Perihelion was 2 Jan 2018 and the 
winter solstice was 21 Dec 2018. This 12 day difference defines the offset of 
the intersection of the analemma loops. When was the perihelion on the winter 
solstice? The perihelion changes in a cycle of 25,800 years. So 12 days gives 
12/365.25x25,800 or 878 years ago. In 1140 AD I would expect a symmetrical 

Of course there is more to this than this simple approximation of orbital 
dynamics. What was the actual date when the perihelion and solstice were the 
same? I offer this as quick answer to the question on the significance of the 
analemma curve intersection.

Regards, Roger Bailey
Walking Shadow Designs

From: Dan-George Uza
Sent: Thursday, April 12, 2018 3:46 AM
To: Sundial List
Subject: Analemma intersection


Tomorrow the Sun will have reached the point of intersection in the analemma 
8-curve. How do you compute the exact time of intersection (i.e. when both the 
hour angle and the solar declination match for two days)? And does it have any 
special significance?




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