Is The Moon Larger At The Horizon? A Moon Illusion Experiment (Video)

(N.Morgan) The moon has has always been cloaked in mystery and has been the focal point of ancient societies and religions.It has also been utilized to keep track of days and time. In this experiment, we explore whether to moon is larger at the horizon or if this is a mere visual illusion.We tend to think that the image of the moon, near the horizon, is larger than when the moon is high in the sky. We can check to see if the moon is magnified, near the horizon, by using a digital camera and Paint.Net software. Also, a tripod may be needed to stabilize the camera.

What we need to do is take a picture, of the moon, near the horizon and another picture, of the moon, when it is high in the sky. We can use Paint.Net to compare the two pictures to see if the moon, near the horizon, is larger than the moon high in the sky. Both pictures must be taken by the same camera and have the same zoom, megapixel and aspect ratio settings. These, are two pictures of the August 2014 super moon. These pictures were taken about 70 miles from Toledo Ohio. The first picture was taken, about 45 minutes, after moonrise on 8/10/2014 at 9:08 pm local time. The second picture was taken on 8/11/2014 at 4:43 am local time. Both pictures were taken by a Sony Cybershot DSC-H300 camera at 35x optical zoom, 20.1 megapixels and a 4:3 aspect ratio.

We will start with the picture taken at 9:08 pm. The moon is selected by the Magic Wand. The Magic Wand allows us to select areas of similar color. I’ll select a light area of the moon and then we have to adjust the tolerance until all of the moon and only the moon is selected. This looks good so I will zoom in and verify that we have a nice border around the moon, all of the moon is selected, and only the moon is selected. This looks good, so, we will find the number of pixels that are selected. We find that the area is 1,235,285 pixels square. We’ll go to the second picture. Select the magic wand. Select a light area of the moon. Change the tolerance until all of the moon and only the moon is selected. We’ll then zoom in to verify that everything is selected. I see a little area here that is not selected, so I will modify the tolerance. That is a whole lot better. We have a good border.

Everything looks good. We’ll find that the area is 1,250,923 pixels square. All we have to do, now, is divide the two numbers. We find that the moon’ s image size is smaller nearer to the horizon. This result may be surprising but concurs with the fact, that, at the horizon, the moon is about one earth radius farther away resulting in the moon’s image being about 1.5% smaller. Also, atmosphere refraction can make the image of the moon, slightly, vertically smaller. Does your finding concur with the finding in this video?

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