Celestia Forums

My question, is there a site or program that can help me create more realistic lunar orbits for alien planets based on their size (radius)? I know mass of the planet and moons are key factors but I have no way of determining those variables in celestia. As of now I'm making guesses and decisions based on aesthetics.
Any help is much appreciated.

Reiko wrote:My question, is there a site or program that can help me create more realistic lunar orbits for alien planets based on their size (radius)? I know mass of the planet and moons are key factors but I have no way of determining those variables in celestia. As of now I'm making guesses and decisions based on aesthetics.
Any help is much appreciated.

Sorry... I can't help, but I would very much like to know where one looks
to find such information too. Has to be confined to physics and mathematics though.

Take care, Brain-Dead

Try this-
http://www.bumply.com/astro.html

Tim

fungun wrote:Try this-
http://www.bumply.com/astro.html

Tim

Hey now...
THAT was very useful. Thanks Tim.

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Hi Reiko,

I don't know what degree of accuracy you're looking for, but—if you're reasonably comfortable with math—here are a few books that do a good job acquainting you with orbital theory:

Adventures in Celestial Mechanics by Victor Szebehely
Orbital Motion by AE Roy

Here's a fact that you might find consoling: Isaac Newton supposedly admitted that he was plagued by headaches and insomnia when trying to calculate our own Moon's orbit; and he could only calculate its perigee within about 8%! This is because calculating orbits when only two bodies are involved is easy, but calculating ones when 3 bodies or "n" bodies are involved gets very complicated very quickly. Moon orbits always involve at least three bodies—more if other large planets orbit a star. In addition, the parent planet's oblateness can also be a significant factor. It's one of the parameters that makes our own Moon's orbital "axis" rotate roughly once per decade.

If you're a math-wizard and you want to delve into it very deeply, you can find a lot of info by searching under "Brown lunar theory" and "Chapront lunar theory." You can also find a lot of "theory translated into application" in the book Astronomical Algorithms by the noted computational astronomer Jean Meeus.

Good luck.

By the way, it's always a pleasure seeing the incredible models you create for CELESTIA. Do you ever plan on writing a tutorial describing how you develop such marvels?

Thank you fungun!

VikingTechJPL I'm not a math wizard in any sense but thank you for the help.

There's also a program called AstroSynthesis that you can use offline. It's old, and has a few quirks, but works fine.

http://www.nbos.com/products/astro/astro.htm