Quote:
Originally Posted by Nathaniel B.
No, it isn't. The phase of the Moon is a function of its apparent angular separation from the Sun. The percent of illumination can be calculated as the haversine¹ of the separation angle in degrees.
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You're just repeating my contention that moon phase is dependent on time. For instance, for a last quarter, the moon has to rise 90º before the Sun, and so MUST rise at midnight local time. The last quarter moon can't rise at any other time. And it always sets at noon. (I'm driving myself crazy here trying to visualize this stuff.)
At sunset, the first quarter moon is 90º from the sun, so is at culmination. The first quarter moon, then, MUST set at midnight local time and rise at noon local time. It cannot rise at any other time. And of course, your math verifies that but is meaningless for most humans. Even you, comfortable with the math, haven't made the connection to reality that is vital to understanding whether it is true or false and vital to actually understanding what the numbers mean. Numbers have no meaning in and of themselves. They must be connected to reality.
Just as a check, what time MUST the full moon rise? There is only one time it can rise.
Quote:
Originally Posted by Nathaniel B.
The apparent angular separation can be calculated using the following formula:
θ = acos(sin(Dec1)⋅sin(Dec2)+cos(Dec1)⋅cos(Dec2)⋅cos(G HA2-GHA1)) (Not sure why there's a space inserted into "GHA2". I can't remove it.)
If the Moon was only 10 degrees from the Sun, it should be a crescent. A very thin sliver at 0.7% illumination, but a crescent nonetheless.
¹Haversine = (1-cos)/2
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The problem with trotting out formulas is that they are not intuitively validating. You can use any form of equation you wish and it looks equally valid. Not only that but results of a formula are not intuitively verifiable either. Your calculation could show that the sun rose at midnight, but being a cloud of meaningless numbers, an error picked up in less than a second graphically only yields to calculation by calculation checking of the math. Often the conclusions of pure mathematics are in stark contrast to the phenomenon they describe, and our mental picture of what they describe is entirely bogus.
I apologize, my memory was wrong. The moon, in the SH 4 screenshot I was describing, was rendered a completely wrong size with the crescent moon actually in contact with the disk of the sun. Phase angle would have been less than .001% illumination at those positions.
So here you go, courtesy of Kim Rohnoff from Dutch Harbor and I have the date somewhere but it doesn't matter. This is just a mangling of solar system astronomy so bad it really doesn't matter when and where the shot was taken..... In reality, the sun and moon are essentially the same size in the sky, 1/2 degree, and the moon in that position would not only be invisible, but we would have a partial solar eclipse, which, needless to say did not happen on that day. I believe in this screenie the moon is rendered more accurately to scale than the sun, which is pretty close to double its real size.
SH4 is not an astronomy simulator and any attempt to use it as such is doomed to failure.