Author Topic: Need help with SW moon calculation  (Read 2083 times)

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Offline B Hanson

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Need help with SW moon calculation
« on: October 19, 2016, 11:33:50 AM »
I'm trying to come up with a frequency and duration for Kulthea eclipsing Charon and Orhan. Charon has a 21 day polar orbit and Orhan has a 70 day regular orbit so it would appear to be the times when Charon is approaching and leaving the equatorial region when Orhan is doing the same on the opposite side.

My orbital mechanics are admittedly weak--any solutions?
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Offline Thot

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Re: Need help with SW moon calculation
« Reply #1 on: October 19, 2016, 11:56:39 AM »
I'm trying to come up with a frequency and duration for Kulthea eclipsing Charon and Orhan. Charon has a 21 day polar orbit and Orhan has a 70 day regular orbit so it would appear to be the times when Charon is approaching and leaving the equatorial region when Orhan is doing the same on the opposite side.

My orbital mechanics are admittedly weak--any solutions?

Well, the duration will be dependent on the size of the moons and their respective distances from Kulthea. Does hard data exist for that?

The frequency of eclipses, however, should be every (least common multiple of 21 and 70) days, or 210 days.

Offline egdcltd

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Re: Need help with SW moon calculation
« Reply #2 on: October 19, 2016, 01:25:56 PM »
I'm sure I remember an old post that discussed the orbits of the various moons in detail (because for one thing Charon doesn't really work with orbital mechanics) but I can't seem to find it. Unless I have found it and overlooked it.
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Offline B Hanson

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Re: Need help with SW moon calculation
« Reply #3 on: October 19, 2016, 01:55:59 PM »
Matt mentioned it too. I think i found it but was a dead link.
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Offline egdcltd

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Re: Need help with SW moon calculation
« Reply #4 on: October 20, 2016, 04:15:25 AM »
I think I found it too now, by kmanktelow, with the dead Flikr links.
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Offline Pazuzu

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Re: Need help with SW moon calculation
« Reply #5 on: October 20, 2016, 10:20:44 AM »
I've wondered about this one as well. Mainly as a means of discouraging those players that want to play lycanthropes.

I've always left things kind of vague, but I'm curious as to what the actual mechanical penalties at any given time would apply to a lycanthrope on a world with multiple moons.

Offline terefang

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Re: Need help with SW moon calculation
« Reply #6 on: October 21, 2016, 02:30:20 AM »
from atlas 3rd Ed p144:
Quote
... about Charón is its unique polar orbit ...
... about 21 days to make this orbit, but it has many disturbing perturbations.
... every 149 days Charón is full and at Zenith in a given location ...
... every 10.2 years in certain locales near the equator there is a correspondence of perigee (closest  proximity to Kulthea) and zenith in which Charón hangs huge and red over the night sky.

10.2 years are 170 cycle periods (350*10.2/21)

seams charon has a rather spiralling polar orbit in relation to kulthea,
so calculation of eclipses may be anything but correct
(need a canonical statement from TKA)

simplified:

we need to find a eclipse event in history and check against
the 149 day and 10.2 year periods of charon
vs the 70 day period of orhan from there

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Offline jdale

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Re: Need help with SW moon calculation
« Reply #7 on: October 27, 2016, 01:04:39 PM »
I've wondered about this one as well. Mainly as a means of discouraging those players that want to play lycanthropes.

I've always left things kind of vague, but I'm curious as to what the actual mechanical penalties at any given time would apply to a lycanthrope on a world with multiple moons.

First question would be whether lycanthropes are ruled by one moon or by all of them. There may be a reason only one matters. Or one may aid them and the other hinder.

I also don't take for granted that a moon is necessarily a large orbiting body. It could be a hole in the sky, a window or gateway into another plane, etc. (Although Shadow World is the kind of setting where it is in fact a large orbiting body.)
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Offline starflt

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Re: Need help with SW moon calculation
« Reply #8 on: October 30, 2016, 02:00:05 AM »
I'm trying to come up with a frequency and duration for Kulthea eclipsing Charon and Orhan. Charon has a 21 day polar orbit and Orhan has a 70 day regular orbit so it would appear to be the times when Charon is approaching and leaving the equatorial region when Orhan is doing the same on the opposite side.

My orbital mechanics are admittedly weak--any solutions?

Well, the duration will be dependent on the size of the moons and their respective distances from Kulthea. Does hard data exist for that?

The frequency of eclipses, however, should be every (least common multiple of 21 and 70) days, or 210 days.

From the Master Atlas, Second Edition, pages 19-20:
Orhan is just over 3,500 miles in diameter and orbits nearly on the ecliptic at a distance of 270,000 miles.  Varin is just over 600 miles in diameter and orbits 125,000 miles from Kulthea.  Charon orbits 190,000 miles away in its polar orbit and is only 350 miles in diameter.  Mikori is just under 100 miles in size and is 520,000 miles away.  Finally, Tlilok is 40 miles in diameter and orbits Orhan (no orbit size given).