Category Archives: Spotlights

May 22 and 23 at Senkoku-ishi

May 22, the second day of the dashed spotlight.

Today, the dashed light is clearer than it was yesterday. The bottom dash is slight, but it hits the corner. From tomorrow the width of this light becomes thicker and stronger; the light can be regarded as a dotted line until about the fifth day, the 25th of May.




May 23, the third day of the dashed spotlight.

The observation is impressive today. A dash starts appearing one by one from the top. It takes about three minutes for up to six dashes to appear (see closeup below).


この三角状の石面の凹凸も計算されているのでしょうか!? 完全に遊んでますね。

Is the roughness of this triangular stone surface deliberate? It plays perfectly!


The dashed lights move downward. Approximately 3 minutes until the sixth dash appears. The six dashes will eventually disappear, one by one from the bottom. The show time of the dashed line spotlight continued for 30 minutes after it started.




Iwaya-Iwakage Spotlight, April 2017

April 22 was a special date on the Kanayama Solar Calendar. It is one of the astronomical cross-quarters, a yontobun date, a half-angle date. On this day, the sun’s path is halfway from that of equinox to summer solstice, and the solstice is about 60 days away. The Kanayama calendar makes observations on the four yontobun dates. 

Last year, the spotlight on the floor of the cavern that appeared on 7/22 vanished after striking the Sekimen-ishi on 10/23 as the sun headed south for the winter. This was reported in a previous post. Now the days are getting longer since the sun is returning to the north. And the spotlight has returned!

The spotlight returned on 2/19, and its path on the floor of the Iwaya cavern has been daily moving from north to south as the sun’s path in the sky changes daily from south to north. The spotlight will soon disappear on 5/21, when the light show at Iwaya-Iwakage ends. On that date light returns to Senkoku-ishi down the hill from Iwaya. Then Senkoku-ishi carries on the job of observing the sun over the summer season.

On April 23, 2017, Chika-san visited Iwaya-Iwakage. She took many photos of the movement of the spotlight on the floor of the Iwaya, as it moved from left to right for the viewer, which is from west to east, as the sun traveled in the sky from east to west. She shows how it began as a speck, grew into an oval shape and then shrank toward the end when only a streak of light on the vertical rock pointed to where it was last seen.

Iwaya 0423 Synopsis PDFPlease refer to page 52 of the Kanayama Megaliths Guidebook. Note the red line labelled: 11:30  8/20  4/22  Track of the spotlight. That is the line she was tracking. We thank Chika-san for these photos which give us a visual summary of the start on the floor (marked with observation lines) until disappearance of the spotlight on the rock at the far right.

The 14 photos shown were taken at the following times, ten minutes apart in the middle, a minute or two apart at beginning and end:

11:34     11:35     11:36     11:38

11:40     11:50     12:00     12:09

12:21     12:30     12:41     12:50

12:52     12:53


March Equinox 2017 – 5. March 20

In this last of the five spring equinox posts, we show you Sugisaka-san’s time-lapse photos on the day of spring equinox, March 20. We begin at 9:24 and show photos every 3 minutes, until time 9:48, while the last three photos were shot at 9:52, 9:54, and 9:57.

Following the sequence of twelve photos, we take a closer look at the oval spotlights at times 9:35 and 9:36. This is when the shape of the spotlight best matches the shape of the stone tool. And this conclusion matches with the photo at the bottom taken by Chika-san at 9:35:30.

Sugisaka March 20Ovals 320Chika 0320 93530



March Equinox 2017 – 4. March 19

On March 19, 2017, Kazuo Sugisaka took time-lapse photos of the Iwaya-Iwakage spotlight from high above looking down. We can watch the movement of the spotlight and how the shape changes. The first photo was taken at 09:21, the second at 09:23, and the subsequent photos at four-minute intervals. The last one was taken at 09:51.

Sugisaka 319


March Equinox 2017 – 3. March 20 Oval Spotlight

Spring equinox 2017 occurred on March 20 at around 7 pm in Japan. Chika-san has provided photos of the changing spotlight patterns on the floor of Iwaya-Iwakage. This time, she concentrated on the change in the shape of the spotko as it went from oval to triangular. It is fascinating that the same beam of sunlight can be so shaped by the megaliths!

We start with this photo taken at 9:21 on March 20 as the spotlight first appears as a partial oval on Stone a. Notice the right-angular carvings on the stone. They are meant as a kind of grid for tracking the movement of the spotlight during equinox time. See Guidebook, page 53.

The next three photos were taken at 9:25, 9:30:00 and 9:35:30 am on 20 March. They show the progression of the oval spotko on Stone a, toward our right which is east (as the morning sun moves westward). An oval stone measurement tool has been discovered inside Iwaya. We had suspected that its purpose is to serve as a template for the spotlight shape and size. So the oval stone was placed on Stone a at seemingly appropriate places. See pages 52 and 53 in the Guidebook.   

By time 9:43, the spotko has moved off Stone a and is starting to elongate. Time 10:23, the shape is now a triangle. An equilateral triangle at 12:02, a more acute triangle at 12:30. This is the triangular shape we saw in the previous post. And so, we have seen how the shape has changed from oval to obtuse to equilateral to acute triangle in the course of less than four hours.

In the next two posts, we show you time-lapse photos of the oval spotlight on March 19 and March 20.

We conclude that the oval stone was intended to serve as a template for the equinox observations on stone a. The construction of the megalith chamber and the associated markings and tools are an indication of the high sophistication of the ancient people who built this megalithic site in the mountains of Kanayama.

March Equinox 3 Photos only.pages


March Equinox 2017 – 2. Triangular Spotlight

Chika-san took photos in Iwaya-Iwakage on March 18, 2017, two days before the spring equinox. We showed you ten photos of the Iwaya opening, in Part 1. Here are ten spotko photos which correspond to those ten photos of the Iwaya opening. You can see the changes in the shape of the spotlight over the same 45-minute interval from 12:25 to 13:10. As more light is blocked by the middle megalith, the spotlight becomes narrower until it vanishes completely.

  Spotko 318



March Equinox 2017 – 1. Spotlight Opening

Spring has arrived at the Kanayama Megaliths! Its official arrival date was March 20, 2017 at around 7 pm in Japan. There is an interesting light show in the chamber of Iwaya-Iwakage. We have a series of posts with photos contributed by Chika-san and Sugisaka-san, volunteer observers of the Megaliths.

We have been interested in the varying shapes of spotlights in the caverns at Senkoku-ishi and Iwaya-Iwakage. Nominally, the basic shapes at both sites is a triangle. However, as the sun moves across the sky, the spotlights change their shapes. The shape of a spotlight is due to the sunlight entering a chamber through the opening between megaliths. In other words, the arrangement and the shapes of the megaliths themselves, together with the location of the sun in the sky, determine the shape of a spotlight.

We have an opportunity to study the spotlight in the Iwaya-Iwakage cavern. Chika-san was there two days before the spring equinox of 2017, and then on the equinox day itself. We show you a series of photos that she took of the opening where the sunlight enters to create a spotlight on the Iwaya floor. Changes are subtle, yet significant. The photos were taken at intervals of five minutes, beginning at around 12:25 on March 18, 2017, and ending at 13:10. We will in the next post show you the spotlight patterns on the floor of Iwaya.

Spotlight opening 318 2017