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    Re: Daytime Photographs of Aldebaran and Sirius
    From: Frank Reed
    Date: 2016 Jul 31, 12:42 -0700

    Bob, I think the phrase "hot pixel" is used both to describe temporarily lit up pixels in the detector array as well as permanently lit up pixels. So either way is legit.

    I have tried to set up Stellarium (get it at stellarium.org if you haven't yet) to show the sky from near Edmonton at the time indicated on your photo. I'm attaching a screen capture of that with a circle added to highlight the position of Aldebaran. As you can see, Aldebaran's position, unfortunately, doesn't match the location of that apparent star in your photo.

    The position of Aldebaran makes sense if you think about it. We know that the Moon occulted Aldebaran some hours earlier as seen from a few thousand miles south of your location. So from from your location near Edmonton in Canada (that's right, isn't it?), Aldebaran would have passed about a quarter of a degree above the Moon's north pole (the northern "horn" of the crescent). After that, the Moon continued to move across the celestial sphere due to its daily motion and also (to a much smaller extent) due to its changing parallax in altitude. The Moon's daily motion proceeds in a direction nearly perpendicular to the horns since that directionpoints to the Sun and since its orbital inclination relative to the ecliptic is only 5.2°. So if you slide the Moon across the sky away from Aldebaran for some hours, then Aldebaran has to end up "in the Moon's wake" behind it, trailing more-or-less directly behind the northern "horn" of the crescent.

    Frank Reed
    Conanicut Island USA

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