2016 Winter Solstice Observations.   2. Solar Calendar Simulator

Ed. Note:  In our earlier post https://iwakage.wordpress.com/2016/11/13/533/ we described the Solar Calendar Simulator at the time of the October 23, 2016 observation sixty days before the winter solstice in Iwaya-Iwakage. Here, we present the accurately simulated solar direction on winter solstice day after we returned from observing the sun from Higashinoyama.

Winter Solstice 2016.12.21   再現館 Seigenkan Simulator Building.  In the early afternoon, we rested for a while at the Solar Calendar Simulator.


3419349dThe sunbeam is now hitting the center of the target board at the lowest part of it. It is 13:08; it is still a little early for the simulation. This simulator also reproduces the light of winter solstice at Iwakage 60 days prior to the solstice.

13:26  Perfect! The sunlight shines in exactly at the orientation SW 24°33’ on the face of the board that simulates Iwaya-Iwakage. (It is azimuth 204 deg 33 min in the southwest direction, as we know from astronomical software.) The simulation is exactly right!


This device was made in modern times and corresponds accurately to the movement of sunlight. The light will hit the same place tomorrow and the day after because it is around the winter solstice when the sun’s path does not change much from day to day.

If this were a spring equinox day, you would see the light moving rapidly 1 to 2 cm per day toward the front. Do you know why? If you understand this, you can see why it can be applied to leap year observations!

The simulator hall shows the foundation of archaeological astronomy in an easy-to-understand manner. For modern astronomy, this is a blind-spot.

Next:  Part 3. Iwaya-Iwakage and Senkoku-Ishi



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