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Yes, one of the key stars of the "W" of Cassiopeia is missing. It's Schedar, which is also the singular "Nautical Almanac 57" star in Cassiopeia. It's just gone.

Here are a couple of images I made while trying to illustrate this anomaly yesterday. Note that the file "cass-anomaly-compare.gif" should animate, flipping back and forth between a version of the original photo and an overlay created from the previous Stellarium image. If it doesn't animate, you may want to download it and try opening it with a different tool.

I saw this happen once before, about twenty years ago, in an entirely different technological setting. I have probably told this story before. Sitting under the dome of the Treworgy Planetarium at Mystic Seaport Museum, I was listening to Don Treworgy doing some star-hopping for a navigation class. Casually scanning the sky, I noticed that Arcturus was simply missing. How do we lose one of the brightest stars in the sky?! My background with this system ruled out an obvious possibility. All of the displayed stars get their light from a lone powerful light bulb. This was an old Spitz planetarium projector, and most of the stars were produced by simple pinholes of various sizes in the central projector box. The brightest stars, a few dozen in total, were focused by small lenses that looked a bit like bug eyes on the projector. Don was speechless for a minute! We decided after a little thought that there was probably an actual bug sitting on one of the "bug eyes". A big fat fly had landed right on top of the Arcturus lens and was basking in its glow.

I don't think flies can explain this Schedar disappearance act... I'm relatively confident that it's happening in software on the iPhone, even before the image was saved. The "night mode" on these phones is relatively sophisticated, and it does a nice job "cleaning up". The "jitter" that you would expect from wobbly hands in an exposure that can last for a second or more does not usually appear in the images. So I suppose there's something like automatic "stacking" taking place. I'm sure there are plenty of good guesses from the astrophotography experts on the underlying software tricks here. But knowing Apple, I also suspect that they have not produced a real technical document or explanation of the algorithms. There's money in it, and Apple is "smart" about guarding its treasure.

Frank Reed

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