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Thread: Ep. 234: Lunar Phases

  1. #1
    Join Date
    Jul 2003

    Ep. 234: Lunar Phases

    The Moon is a stark reminder that we actually live in a Universe filled with stars and planets and moons. The changing phases of the Moon show us the relative positions of the Earth, the Sun and the Moon as they interact with one another. Let's learn about the different phases, the geometry of the whole system, and some of the interesting science wrapped up with our fascination of our only natural satellite.


  2. #2
    Join Date
    Oct 2011
    Fresno, CA
    I listened to this episode earlier in the week and I would like to call everyone's attention to an excellent freeware computer program that can be used to animate the lunar librations, among many other features. The program is called Virtual Moon Atlas (VMA) and it was written by the same guy (Patrick Chevalley) who wrote the excellent freeware planetarium program, Cartes du Ciel (CdC). You can download VMA at and CdC at There is a lot of good freeware astronomy software available and these are two of the best.

    Hereís how to animate the lunar librations in VMA:
    1. On the panel to the right of the Moon display, click the [Ephemeris] tab.
    2. Below the Date and Time data entry boxes are four buttons: [<<], [<], [>], [>>]. These buttons run the clock backwards fast, backwards slow, forwards slow, and forwards fast, respectively. Click and hold one of these buttons to animate the libration as well as the lunar phase. Note the moving red arrow along the limb, which shows the point of maximum libration.
    Itís that simple.

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