Uranus's Tilt

[Sen]

When I go to Uranus, I've noticed that it is not tilted at it's 97.722 degrees, even though it is specified in the solarsys.ssc file. I am running windows vista home premium with ATI Radeon 3100 graohics, using celestia 1.6. Here is the Uranus section of solarsys.ssc:

Code: Select all

"Uranus" "Sol"
{
   Texture "uranus.*"
   Color [ 0.75 0.85 1.0 ]
   HazeColor [ 0.5 0.8 1.0 ]
   HazeDensity 0.2
   Radius 25559 # equatorial
   Oblateness 0.0229

   CustomOrbit "vsop87-uranus"

   # Overridden by CustomOrbit
   # EllipticalOrbit
   # {
   #    Period           84.0139
   #    SemiMajorAxis    19.1913
   #    Eccentricity      0.0472
   #    Inclination       0.7699
   #    AscendingNode     74.230
   #    LongOfPericenter 170.964
        #    MeanLongitude    313.232
   # }

   Atmosphere {
      Height 130
      Lower [ 0.75 0.85 1.0 ]
      Upper [ 0.5 0.8 0.9 ]
      Sky [ 0.6 0.7 0.7 ]

   }

   BodyFrame { EclipticJ2000 {} }
   UniformRotation
   {
       Period         17.24  # System III (magnetic field)
       Inclination    97.722
       AscendingNode 167.647
       MeridianAngle 331.13  # correct System III prime meridian
   }

   Albedo            0.66

   Rings {
      Inner  41837
      Outer  51179
      Texture "uranus-rings.png"
   }
}

[Chuft-Captain]

Your SSC code appears to be correct, and I cannot see any problem on my system (in build 4814):

uranustilt.jpg

Can you click on this celURL and capture an image of what you see from the same viewpoint (with planetographic grid enabled): cel://Follow/Sol:Uranus/2009-08-12T11:54:38.22078?x=AEXHriY9egU&y=0CjP1U/NGg&z=8NJFqucJcwE&ow=0.785463&ox=0.0401735&oy=-0.617115&oz=0.0245392&select=Sol:Uranus&fov=21.6458&ts=1&ltd=0&p=0&rf=1917751&lm=2&tsrc=0&ver=3

[BobHegwood]

Just FYI...

The planet is tilted accurately on my system using 1.6.0
Have done nothing special to account for this.

Having said that though, there used to be a problem using CEL scripts
to arrive at the planet with the tilt enforced. In other words, having
arrived at Uranus using a goto, a script would have to rotate the planet
itself in order to maintain the proper perspective.

Is this what might be happening still?

Thanks, Brain-Dead

[ajtribick]

Well Uranus is currently in Spring/Autumn (depending on what hemisphere you're in), it isn't pointing either pole at the Sun right now.

Fast forward to the 2030s and you have the situation where one pole points towards the Sun, one points away.

[Sen]

I'm not running any scripts, and going to 2030 does not change anything. (I tried several reference frames, all of which still showed uranus as being on a "normal" tilt, that is, not inclined at 98 degrees) Attached is an image of what I'm seeing. I really don't know why this is happening, as you can see in the picture, the grid and the axis are lined up as if Uranus is not tilted at all. Is there perhaps a way to modify the file to make it tilt correclty, or am I just crazy?

[selden]

There was a previous report of a similar problem at viewtopic.php?f=3&t=11601 but it was seen with a botched compilation of an older version of Celestia for Linux, not for a standard distribution of Celestia for Windows. This is very strange.

Is there any chance that you have an Addon installed which modifies some of the planetary definitions?

I suggest downloading a fresh copy of the Celestia v1.6.0 installer from http://sourceforge.net/projects/celestia/files/ and installing it from scratch. Don't uninstall the current version, instead, it might help to tell the installer to put Celestia into a folder named C:\Celestia and not into Program Files.

I'm just grasping at straws here...

[Sen]

Well, when 1.6 was released I downloaded it onto a disk (I have dial-up, so I downloaded Celestia at a friend's house.) I installed it on my desktop, and when I finally purchased my laptop, I used the same disk to install Celestia on it. So both versions came from the EXACT SAME installer. The Celestia on my desktop, I noticed, displayed Uranus correctly. So I copied the ssc file from my desktop and compared it with the one on my laptop. I couldn't see any differences, but I replaced the one on my laptop with the one from my desktop. And lo and behold, it worked. How or why I have no idea, but I'm not complaining.

[selden]

Sen,

Thanks for letting us know how you fixed the problem.

Your fix suggests to me that the line in the SSC which specifies the planet's tilt was corrupted during installation, so that Celestia ignored it. Being paranoid, I'd wonder if there might be a hardware problem somewhere in the laptop.