Gemma Frisius -Sunrise Ray Observed

Gemma Frisius is the large "Mickey Mouse"
head  (not including ears)   in the image above
by Ann Ditmer.       Full Dittmer image here

The following report on a sunrise ray was submitted to the Lunascan Project by Brien Stratton, on Sun, 16 Jul 2000 12:33:04 -0400.  Gemma Frisius is an 88 km crater with a damaged wall. (Refer to your copy of the Rukl atlas,  Section Directory 66. For a large LO image (with Gemma Frisius in the upper right), click on the link below:

Please submit any improved image links that might be appropriate for this crater or region to this Project address:

Francis Ridge
The Lunascan Project


I would like to report a sunrise ray I observed in the crater Gemma Frisius.

I will explain what I saw:

On Friday July 7, 2000 at approximately 7:00 Eastern Standard Time, I was observing the moon at the terminator. I have a 20" Obsession dobsonian and was observing at my parents house which is north east of the city of Toronto, Ontario in Canada.

I was looking at the Gemma Frisius crater and I saw a triangle of light that, according to Rukl map # 66 of his atlas started at the middle of the crater on the eastern side and then forming a triangle that got wider as it went to the western side, illuminating 2 or 3 small craters in the floor of the crater. The triangle of light was not ordinary light illuminating the crater floor. It was very thin and shadowy and seemed to hover over the crater. It was visible for about a half hour, but it may have been visible for awhile before I saw it. This ray was so obvious that it stood out. Anyone with a telescope would have seen it.

I did not know what it was at the time, so I assumed it was a common occurance and didn't study it to death. This triangle of light was also witnessed by my mother, Phyllis Stratton, who also confirmed it. It appeared as light coming through a hole in the crater wall and shining like a flashlight into the crater. When I went to the description in the atlas about the crater it says it has a broken wall, which puts all the pieces together.

Another strange thing I saw was two bands  of darkness in the triangle which were perpendicular to the triangle almost like dark bands in a spectrum of a star. They were spaced fairly evenly out in position in the triangle. They seemed to be almost part of the light ray triangle. I thought the bands were  hidden details on the crater floor that the ray was illuminating, but when I looked at the chart there was no correlation.

I am wondering if anyone else witnessed this sunrise ray, and also if you have seen these bands in other sunrise ray events, and finally do you know what they represent?


Brien Stratton

This web page was created by The Lunascan Project. The Home page is located at: