Due to the elliptic shape of Earth's orbit around the Sun, the apparent diameter of the Sun varies throughout the year. With digital analysis of a number of images at a given date, the effect can be demonstrated with a digital single lens reflection camera (DSLR) and a standard telephoto lens even over a few days. In the analysis, the influence of image brightness and atmospheric refraction on apparent Sun size and shape have to be removed to reach the accuracy that is required.

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