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A Info on the motion of the moon

  1. Aug 10, 2016 #1
    I am looking for concise information for two of various factors that affect the motion of the moon.
    I understand the 5 degree tilt of the moons orbit and the progression of the nodes. also the effect of the tilt of the earths axis and the eccentric orbit of the earth around the sun. I an looking for the 2 next greatest effects, their period and the value or percentage variation. can anybody direct me where to look or advise me as I do not find much that is specific on the web. I need this info as I am building a Moon ris/ set mechanism for a clock. You can see it herehttp://[URL="http://www.my-time-machines.net/astro_index.htm"]www.my-time-machines.net/astro_index.htm[/URL] [Broken] you may have to page a bit but there is a lot of info on the clock here.
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Aug 11, 2016 #2


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    I can't help you with your question, but that clock your are building is impressive! Good luck with your project.
    Last edited by a moderator: May 8, 2017
  4. Aug 11, 2016 #3


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    There is also precession of argument of perigee. It has a period of about 9 years.
  5. Aug 11, 2016 #4

    Wow, what an incredible piece of engineering. I love the Victorian/Edwardian feel it has.

    Argument of perigee will determine , amongst other things, whether there is a total or annular eclipse. Argument of perigee is the direction of the moon at point of closest approach. When it's opposite ( apogee ) aligns with an eclipse, it produces an annual eclipse.

    Have you included the nodal precession and the precession of the earth's orbital line apsides ( the time/date of perihelion drifts a little each year ) and the equinox drifts. The drift in perihelion is about 1 day in 72 years from memory or about 20 min each year.

    Then there is the pull of Jupiter ( and Saturn ) which means perihelion comes a little closer

    The data plotted here was recovered from JPL ephemeris.

    That change is getting quite small and may be less than the resolution and stability of your mechanics.
  6. Aug 11, 2016 #5
    Thank you Fizzy
    Tre Edwardian/Victorian feel was a requirement. I have the eclipses taken into account on the tellurian. As you say, there is the mechanical tollerence of the mechanism to take into account. What I am trying to achieve is a visual universe that can be viewed from various angles or perspectives. there is still a planisphere and an orrery to be attached to the clock. So one can see the universe from the earth and then move outward and see the earth and moon in the tellurian and then further and see the whole solar system. I am working on the moonrise/set dial so am looking for factors that affect the time of moon rise and set.
    what I would really like a a set of graphs giving the magnitude and frequency of the first 4 largest factors that affect the time of moon rise and moon set.
    I have to decide what to include to give me results that portray the moon on the dial in such a way that when you look our you window the moon rise will occur within a few minutes of where the clock dial says it should. This is a visual portrayal, not an observatory instrument. so we have a tolerance of say 10 minutes either way but do not want an accumulating error of more than ten minutes a year.

    Tony I really like that animation. I have to translate that motion into the effect it will have on the time of moon rise and moon set in Chicago! Add into that motion the "tilt of the earth's axis" effect .I can cope with fairly complex design concepts( I designed the rest of this clock) but the moon rise / set dial is getting the better of me.
  7. Aug 11, 2016 #6
    Here are some photos of the clock. P1050435.jpg P1050433.jpg P1050435.jpg P1050435.jpg P1050433.jpg P1050435.jpg
  8. Aug 11, 2016 #7


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    I felt proud of myself this summer when I fixed my father's Grandfather Clock, including the moonphase display. It's a 1934 Hershede. But your project is in a different league! I hope you come back here and post pictures when you're finished.

    I don't know if this will help you, but I can make you a simulation that will output just about any number related to the Moon's position, including orbital elements and position and velocity vectors.

    Here's an example: http://orbitsimulator.com/gravitySimulatorCloud/simulations/1470952670108_moonData.html

    The output can be customized, perhaps as columns of numbers that you can paste into a spreadsheet so you can graph it.
  9. Aug 11, 2016 #8


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    Wow! That's like my Hershede clock x 1000!
    You should put a live webcam on that when you're finished.
  10. Aug 11, 2016 #9
    Thanks Tony There are many videos in this website :www.my-time-machines.net/astro_index.htm. you can also subscribe to monthly updates.
    it has a demo mode so that you can wind it around at what ever speed you like, Here is my understanding of the moons motions:http://www.my-time-machines.net/astro_11-15.htm.
    Where I have bogged down is that I need to make a ball in the end of a pivoted arm rotating around a dial at approximately the same speed as the moon moves across the sky. At the 3 and 9 o'clock position we have the east and west horizon I must then make a correcting differential that speeds up or slows down the moon for each factor that affects the rise and set time of the moon. So that if the tilt of the earth on its axis introduces a 7 percent advance and retard in rise and set time during the period of a year then I must move the differential housing forwards and backwards by 7 percent once a year. Next we have the 5 degree tilt in the moons orbit. This requires another "correction" at a different period to the first correction , So I place a second differential behind the first with another gear ratio for the moons tilt, So every factor has a period and a magnitude, I need help as to how to find this information out as, you say, in graph form. for each factor so that I can decide how many factors I need to take into account to achieve an acceptable accuracy.
  11. Aug 11, 2016 #10


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    Really an incredible piece of work. That would look pretty awesome in the Smithsonian. :wink:
  12. Aug 18, 2016 #11
    Thank you for the compliments. The Smithsonian does not want it, even as a donation!
    I have managed to find the five factors that I am looking for. What I need to find out is the period and magnitude of the deviation of the following ,The Anomaly, The Evection, The Variation, The Annual Equation and the Reduction. I would be correct in that understand that individually each variation would be a sin wave?
    thank you again for all the response.
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