Category Archives: Spotlights

Leap-year Observation Spotlight of February 27 and 28

金山巨石群 閏年観測のスポット光

Kanayama Megaliths Leap-year Observation Spotlight of February 27 and 28

The topic of this post at the Kanayama blogsite is the leap-year observation at Stone b  in Iwaya-Iwakage. It takes place on 10/14 and 10/15 and is repeated on 2/27 and 2/28.   The photos for 2/27 and 2/28, when the light returns to the stone, are shown .




Of further interest is the ongoing study of the 128-year leap-year cycle. The  measurement of 6 cm was recorded. 

52 years have elapsed in the current 128-year cycle of the Kanayama Megaliths calendar. It will next be revised around the year 2094, 76 years from now. We consider the position of the light (in the photo) is as expected. This is in accordance with the theory described in the Guidebook, page 66, as shown at the top of this page.

The post’s concluding remarks were:

Although it is still cold this year, since the sun is steadily heading for spring, there is nothing to worry about. People in the Jomon period must have grasped the changing period of vegetation as well. Nevertheless, their power to build such a calendar building is great ….





February 19, 2018 Winter into Spring

金山巨石群 冬期120日間終了の光

Kanayama Megaliths 120 Days of Winter Ends 2018 21519

This is our excerpt from the blog posted by the Kanayama Megaliths Research Center at on 2018.02.22. 

The face of the Sekimen stone in Iwaya-Iwakage is lit by a spotlight for five days from February 15 to 19. February 19 marks the end of the 120-day winter season. (The exact number of days was 119.) The 120 days of winter can be divided into the 60 days of Early Winter ending on the Winter Solstice and the 60 days of Late Winter following the Solstice.


The Kanayama blogsite has posted two photos taken on 2018.02.19 at 13:23 and 13:33. Note how well the lower edge of the spotlight matches the edge of the Sekimen. Comparison of the two photos shows that the solar altitude has decreased during the ten minutes lapse, causing the spotlight to move higher “up” the stone face. The spotlight of 2/19 matches that of 10/23, because the sun’s altitude is the same on these two days.


Here is a view of the beam of light entering from the crevice above. Three megaliths form the crevice and shape the sunbeam in exactly the right way.




October 27, 2017 Sekimen-ishi Spotlight


October 27.  This is the last day of the year for viewing the spotlight on Sekimen-ishi. The light will return on February 15 of next year. Although Sekimen-ishi means Sekimen stone, it is not a stone separate from Stone F but rather a projection of the megalith itself. That makes it all the more amazing how well the spotlight matches the shape and size of Sekimen-ishi.


This special day, some of the regulars came and it was fun viewing the spotlight together. We had a splendid light show!


In the afternoon, six busloads of visitors came from a company in Osaka, three buses at a time. They were guided by Ms. Tokuda, Mr. Kobayashi, and Mr. Okudo. They also had the chance to walk the Kinkotsu-meguri through Old Town and have lunch at Hizan. Surely it was quite a memorable experience for the Osaka-ites.





October 23, 2017 After the Typhoon

DSC04680 driving up

Typhoon 21 reached Kanayama the night of October 22. It had been cloudy all week and we were eager to view the spotlight on Sekimen-ishi in Iwaya-Iwakage.

DSC04710 side view of toriiOctober 23.  Monday morning dawned cloudy and rainy, and it seemed hopeless. But the sun appeared mid-morning and we dared to venture out to the megaliths at noon. The drive was fine, until — we got to the last bend in the road. There we were stopped by a roadblock. Due to fallen branches, we could not drive further.

We parked the car and hiked in. It wasn’t far to go. There were many sugi and hinoki branches on the road, but we could walk easily and avoid stepping into rivulets. The walk turned out to be refreshing. The stream that runs into the Mazegawa was full of water and rushing along. We crossed over the Myouken-hashi bridge.


DSC04703 Myouken-hashi sign

We were happy to arrive at the megalith grounds and all was well. The stream there was whiter than we’ve ever seen it.

IMG_2182 KM stream


Megaliths are lovely after a rain. Their surfaces glisten in the sun. Leaves on plants and trees are a brilliant, glistening green. Flowers were blooming on the tea plants. Since tea is a camellia, the flowers of course resembled camellia flowers.

When we got to the entrance to the chamber of Iwaya-Iwakage, we could see the spotlight. Inside, the spotlight was already lighting up the Sekimen-ishi, skimming the face of Stone F, and some of it was spilling off the lower edge. The faithful team of sun and stone created a beautiful sight!





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