Phases of the Moon: Angular Separation Question

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The discussion centers on the angular separation of the moon during its first and last quarter phases, which is 90 degrees. The question raised is whether this measurement reflects the true angular separation or simply the difference in ecliptic longitudes. It is clarified that the 90-degree separation occurs because the earth-moon line is perpendicular to the earth-sun line during these phases. This indicates that the angular separation is indeed a true measurement rather than just a difference in ecliptic longitudes. Understanding this distinction is important for accurately interpreting lunar phases.
kepler
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Hi,

Just a stupid doubt...when the moon is in FIRST QUARTER or LAST QUARTER, their angular separation is of 90 degrees; question: is it the TRUE angular separation or is it the difference of ecliptic longitudes?

Kind regards,

Kepler
 
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First and last quarter moons result from the earth-moon line being 90 deg. from the earth-sun line.
 
That was my initial guess :)

Thanks,

Kepler
 

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