Reconstructing the Straight Path of Transiting Mercury Using AR2542
Taken by Helio C. Vital on May 9, 2016 @
Rio de Janeiro, Brazil
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Details:
A difficulty encountered by many of those who, like us, photographed the transit of Mercury with cameras on altazimuth mounts was how to use the photos to reconstruct the straight path drawn by the planet across the Sun`s disc. However, by realizing that prominent Active Region (AR) 2542 remained approximately still during the 4.55 hours of monitoring (neglecting its 2.5° displacement), it was possible to turn each image by a different angle in order to achieve the same result as if an equatorial mount had been used. Then the actual straight path of the planet becomes evident as roughly illustrated in the first (5-frame) animation, that shows the adjusted positions of Mercury across the disc of the Sun between 12:56 and
17:29 UT. If no such procedure had been applied to compensate for changes in the Sun`s position in the sky (up to 84° in azimuth), the resulting path of Mercury would resemble an Archimedean spiral, like the one shown in the second (6-frame) animation. In both animations, ten photos were stacked to produce each frame. Cloud interference severely reduced contrast, almost erasing AR2542 in most processed images, excepting near mid transit, when it became milder. PhotoScape was used to enhance contrast, turn the stacked images in order to keep AR2542 in the same position and make the animations. All photos were taken with a Sony Cyber-shot DSC-HX300 camera (with a black glass filter for observation of the Sun) positioned on a tripod.
Photographer's website:
http://https://www.flickr.com/photos/98669508@N03/
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