Celestia Forums

Please can anyone help me by explaining which parameters I need to adjust, for example to bring Jupiter’s orbit closer to Mars?

I’m trying to create an Orrery of our Solar System, so that I can clearly display all nine planets on one screen. To achieve this I guess I need to modify the entries in solarsys.ssc, to create false orbits. However, to-date I’ve not been very successful. I want to maintain the planets correct positioning, just artificially adjust their distance from the Sun.

SemiMajorAxis is the value you need to change. This is the distance from the planet to Sol, measured in AU.

Ortolan wrote:SemiMajorAxis is the value you need to change. This is the distance from the planet to Sol, measured in AU.

I believe, your right. But it doesn?t work. I tried on jupiter, but the position won?t change.

Ortolan wrote:SemiMajorAxis is the value you need to change. This is the distance from the planet to Sol, measured in AU.

That works, but only if you also modify the CustomOrbit value as well. For example, to bring Jupiter's orbit next to Earth you need to set the following values:

CustomOrbit "jupiterSomeOtherName"
SemiMajorAxis 1.0000

What is the CustomOrbit value and why does it need to be changed?

You can just comment out the CustomOrbit value (by placing a # at the start of the line) rather than renaming it. Custom orbits are used for the major planets because the kepplerian elements are too imprecise (since they just describe a simple elipse made by a single gravity source.).

The value "CustomOrbit" tells Celestia to use an internal orbit calculation subroutine and not the simple Keplerian orbital parameters that are in the file.

A Keplerian description of an orbit doesn't take into account the gravitational effects of the other bodies in the solar system. It assumes that only the gravitational attraction of the central body matters and that the orbiting body always follows a simple eliptical path.

The internal routines take into account most of the gravitational effects on the various planets so that the orbits are more accurate over a longer time.

I hope this clarifies things a little.

Thanks for explaining things for me, I now have an Orrery!

Immy

It's also interesting to compare sizes by putting all the planets on the same orbit, fairly close to the sun (if you like that sort of thing).

Immy wrote:Thanks for explaining things for me, I now have an Orrery!

Immy

Jmmy, due to my interest on Astronomy school training using Celestia, I was thinking about something of this kind, so could you be so kind to share your solarsys.ssc with your orrery?
If you want, but prefer to send it privately, this is my address:

mc3657@mclink.it

Thank you

Andrea

ANDREA wrote:
Jmmy, due to my interest on Astronomy school training using Celestia, I was thinking about something of this kind, so could you be so kind to share your solarsys.ssc with your orrery?
If you want, but prefer to send it privately, this is my address:

mc3657@mclink.it

Thank you

Andrea

Will do, I'll email it to you as it's quite long.