Eager to take a break from my studies, I ran outside to observe a low, twilight pass of the ISS. Through 7 x 35 Pentax binoculars it looked like a pale copper-colored glistening dot. Due to its low altitude it soon passed behind a tree that was about 100 feet away. When it emerged from behind a large branch it appeared as two distinct dots rather than one!! For several seconds it drifted behind small branches and continued to look like two distinct dots. I quickly realized that, as I see happening when I stereofuse two images to see them in 3D, when things up front look like one fused image things farther away appear as doubles, or vice versa. This doubling effect is something that people that are familiar with looking at stereo images should relate to. I found that the tree was far enough away that the depth of field was sufficient to see both the tree and the ISS in almost the same focus. While the ISS was passing through the branches I found that I could hardly force both my eyes to align on it to see it as one dot. When I did, because of the complex nature and the low contrast of the small branches, I didn't notice that they were then paired. Finding it hard to fuse the ISS into one was peculiar to me because when viewing stereo images I can easily manipulate the angle of convergence of my eyes. Soon I realized that seeing two was desirable because they appeared like the beautiful ISS/Shuttle pair many of us saw recently. Quite a show, albeit a false one. Clear skies, Tom Iowa USA ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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