Monthly Archives: August 2018

Thirty Days After Summer Solstice


At Senkoku-ishi, the dashed spotlight tells us in a dramatic light-show when it is thirty days before and after the summer solstice. The Kanayama Megaliths Japanese blogsite has posted photos from this year’s July dashed spotlight observations. There were torrential rains in Western Japan in preceding days, followed by 39 C = 103 F high temperatures. Yet, many people came who had seen the NHK special on the Kanayama Megaliths just a couple of days prior.


The dashed spotlight could be seen for five days, growing stronger, then thinner. Even on the final day, we could see four dashes.


For other photos and the report in Japanese, please click on the above underlined link. As Shiho Tokuda reminds us in this translation from her blog:

“Because the year is not exactly 365 days, the appearance of light slightly changes even for observations on the same day every year. It is repeated approximately every four years. Although it is related to the leap year, it is difficult to determine a leap year by this observation because the movement of the sun every day as seen from the earth is small. ”

For a more accurate method for leap-year determination (in October 2019, for instance), the Kanayama Megaliths has the leap-year observation in Iwaya-Iwakage.