ISS transit in front of the Sun


Manfred Rudolf




The International Space Station (ISS) orbits around the Earth about 15 times a day. Occasionally, it passes in front of the Sun for a given location on Earth, and on such occasion its outlines can be seen as a dark spot on the Sun.

On Saturday 4 March, such ISS transit should be visible from my garden in Munich (48.11458 n.lat., 11.65799 e.long.) in the late morning hours. Predictions for such transits for a specified location can be seen from various programs including
Calsky or ISS Transit Finder.

The chart below shows the expected trail of the ISS starting from upper right (arrow) to the lower left, with timemarks from 11:24:38 to 11:24:42. It can be seen that the ISS crosses the Sunīs disc between 11:24:39 and 11:24:40 (Chart created with Guide 9).




Unfortunately, the Sun was hidden behind thick clouds on Sat 4 March morning. Occasionally the Sun was not visible at all, and it was impossible to properly focus or adjust the exposure time because of the clouds passing in front of the Sun. Nevertheless a video has been recorded using a 500mm telephoto lens and a ZWO ASI 174MM camera. The image below which is a still image from the video shows tiny ISS (angular diameter 40 arcseconds) in front of the Sun. You may find the ISS to the lower right at the intersection of the two white lines near the solar limb:



The duration of the ISS pass in front of the Sun was only 0.6 seconds, so it is hardly visible in the video. The original video has been recorded with 215 frames per second, replaying this video with standard frame rate slows down the movement of the ISS to about 10% of the actual transit speed.

Here you can download mp4 video files of the transit in real time (ca. 10 MB) and also the slow version (ca. 10 MB).



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