Re: Comparing point sources to resolved sources

From: Tom Wagner (
Date: Tue Dec 31 2002 - 01:48:28 EST

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    Rob and others,
    Thanks for your help. :~)
    The question of comparative brightness between stars and non-stars,
    especially as seen through any of a number of different optical instruments
    is dependent upon so many variables, some of which are physiological, that
    it's an almost hopeless task to resolve. (Pun intended.) I debated a similar
    topic on another list until I ran out of time and finally gave it up,
    although I can say that I learned some interesting things about visual
    perception in the process.
    What I really do wish I knew was how to mathematically predict the relative
    brightness of a satellite compared to the surface of the moon as seen
    through a particular optical setup. But now that I think about it, that too
    is probably a task that has little purpose. As was previously mentioned, all
    the satellites in daylight are going to be brighter than the moon anyway. I
    think I'll just leave it at that.
    It just bothers me that I (and many many others) have the misconception that
    the moon's surface is much brighter than it really is. Up to a magnitude -12
    after all! I have long known it has the albedo of asphalt and I've often
    told people that it looks bright only because it's against a black
    background. I just never thought about a sunlit satellite as being brighter
    than the moon's sunlit surface. I was surprised at what I saw the other day
    and got puzzled.
    There is a fascinating reason why the full moon is so extra "bright." See
    to read why.
    P.S. Today my wife was upset that I drove the car on gravel roads and got it
    all dirty. When I said I did it while searching for the spot to see the ISS
    cross in front of the moon, she said, "Haven't you seen that thing before?"
    .... [Sigh] .... I was speechless.
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