Uranus rotation plane

[diogen]

Hi there! Sorry to interrupt you but with all my respect to Chris & Ko, Uranus and its satellites rotation plane (according to astronomy data) is almost perpendicular (and rotates counter-clockwise) to ecliptic (90+ degrees). But in my 1.4.1 Mandriva 2008 version it is in the ecliptic... btw, Miranda goes contrary to others, why?..

[selden]

diogen,

I'm a little confused by your description of the problem.

Uranus is tipped over so that its rotational axis is almost in the plane of the ecliptic. It is not perpendicular to the ecliptic like the other planets. The plane of its equator is perpendicular to the plane of the Ecliptic.

The orbits of Uranus and its moon Miranda are defined for Celestia in its file Celestia/data/solarsys.ssc

If I'm interpreting your description correctly, your symptoms suggest that someone has edited that file. You should discuss the issue with whoever did those edits.

Official versions of solarsys.ssc are available at http://celestia.cvs.sourceforge.net/cel ... c?view=log

For example, the orientation of Uranus is defined by the lines

Code: Select all

   RotationPeriod        17.24 # System III (magnetic field)
   Obliquity             97.81
   EquatorAscendingNode 167.76
   RotationOffset       331.18 # correct System III prime meridian


(these were taken from Celestia v1.4.1 final for Windows)
The Obliquity entry defines the tilt of the planet relative to the perpendicular to the Ecliptic. As you can see, Uranus should be tipped over so that its polar axis is slightly less than 8 degrees from the plane of the Ecliptic.

Here is what I see on my Windows system when viewing Uranus and Miranda with Celestia v1.4.1 final. It seems to be correct.

[diogen]

Thanks a lot for your prompt reply! Yeah, I obviously should say 'its equator plane is perpendicular', you are quite right. Nevertheless, you've catched up the problem. Your screenshot is what I expected to see, but in my case this was like for other planets - an axis is perpendicular, so satellites go in the ecliptic plane clockwise, except of Miranda going counterclockwise. I'll check the file you suggested.
btw, why Phobos and Deimos might not be visible except as points from far away? I'm using precompiled Mandriva celestia-1.4.1-8mdv2008.0.i586.

[selden]

diogen,

Phobos and Deimos are binary CMOD models. Some copies of Celestia v1.4.1 built for Linux were built with the wrong compiler options. Those versions of Celestia cannot display CMOD models.

This problem is discussed in the thread at
http://celestiaproject.net/forum/viewtopic.php?t=9605&

You can either obtain a copy of Celestia v1.4.1 which was built using modified compiler options
or obtain a copy of Celestia v1.5.0 built from the current (beta) CVS code using standard compiler options
or rebuild one of them yourself.

Celestia v1.4.1 has been out for more than a year. I suspect that a rebuilt version for your Linux distribution already is available somewhere.

[diogen]

Thanks, Selden! I've already discovered the point. I changed models in solarsys.ssc onto *.3ds, and it works. Anyway, thanks for explanation, why it is so. As to new rebuilt, mdv2008.0 has been issued only 2,5 weeks ago. I have no idea why thay have not compiled this with right options though... Sorry for silly question, where to find 1.5.0pre (rpm or src)? Sourceforge?

[selden]

The Celestia development team does not try to create RPMs or the equivalent. There are too many variants. Celestia's sourcecode is available by using CVS to download it from SourceForge. e.g.

Code: Select all

cvs -z 3 -d:pserver:anonymous@celestia.cvs.sourceforge.net:/cvsroot/celestia checkout celestia

but you also need to install the development versions of several support packages.

There are several threads discussing how to build Celestia under various Linux distributions.

Ubuntu: http://celestiaproject.net/forum/viewtopic.php?t=11077&
Kubuntu Feisty Fawn: http://celestiaproject.net/forum/viewtopic.php?t=11055&
KDE/gcc 4.1: http://celestiaproject.net/forum/viewtopic.php?t=10575&

and others...