Celestia Forums

Posted: **25.11.2006, 08:24**

Can someone please review my code for the ternary star system. In Celestia I can see the first barycenter orbit, but nothing else seems to display. I am probably missing something obvious

Thanks
-Matt-

Code: Select all

# Sekgnai ABC          

Barycenter "Sekgnai AB-C Barycenter"     
{          
    RA      290.3     
    Dec     -38.4     
    Distance  12620     
}          
  
Barycenter "Sekgnai A-B Barycenter"     
{          
   OrbitBarycenter "Sekgnai AB-C Barycenter"     

   EllipticalOrbit {          
      Period          10768.5049     # Years
      SemiMajorAxis     258.6597665  # AU
      Eccentricity        0.4     
      Inclination         0.25     
      AscendingNode       0     
   }          
}          

"Sekgnai A"          
{          
   OrbitBarycenter "Sekgnai A-B Barycenter"     
   SpectralType     K1V     
   #Mass            1.75E+30     
   Radius           668590     

   EllipticalOrbit {          
      Period            0.012411373     # Years
      SemiMajorAxis     0.032096158     # AU
      Eccentricity      0.011     
      Inclination       0     
      AscendingNode     0     
   }          
}          

"Sekgnai B"          
{          
   OrbitBarycenter "Sekgnai A-B Barycenter"     
   SpectralType     K2V     
   #Mass            1.73E+30 # Years
   Radius           666505   # AU

   EllipticalOrbit {          
      Period              0.012411373     
      SemiMajorAxis       0.032465079     
      Eccentricity        0.011     
      Inclination         0     
      AscendingNode     180     
   }          
}          

"Sekgnai C"          
{          
   OrbitBarycenter "Sekgnai AB-C Barycenter"     
   SpectralType     F9V     
   #Mass            2.10E+30     
   Radius           710000     

   EllipticalOrbit {          
      Period        10768.5049   # Years
      SemiMajorAxis   428.728563 # AU
      Eccentricity      0.4
      Inclination       0.25
      AscendingNode   180
   }     
}

Posted: **25.11.2006, 13:08**

a. you forgot to put quotes around the SpectralType value

b. you have omitted magnitude specifications:
one of either AbsMag or AppMag is required.

c. It's not required, but you might include the prefix Star for clarity.

Posted: **25.11.2006, 19:34**

selden wrote:a. you forgot to put quotes around the SpectralType value

b. you have omitted magnitude specifications:
one of either AbsMag or AppMag is required.

c. It's not required, but you might include the prefix Star for clarity.

Thanks Selden, that did the trick.

A) I didn't even notice that I missed the quotes. Like I said something obvious.

B) I looks like in the 1.5 branch AbsMag or AppMag IS required, with out them the star fails to appears, but the orbits show up. This might just be a bug in the dev branch I got.

do you know what is the easiest way to calculate the AppMag given the stars size, type color, etc...

C) I am not sure what you mean by this?

Thanks again.

BTW does this system look plausible so far?

Posted: **25.11.2006, 19:52**

In 1.4.1, at least, a missing magnitude generates an error message in the console log. I forgot to check for that when I was running v1.5 with your stc file. I'm surprised it draws orbits -- that's what I'd consider a bug. Maybe it's a feature

I really don't know the algorithm that one should use for determining what the AbsMag of a star would be. One quick, if less satisfying, method is to look at Celestia's list of nearby stars in the "Star Browser" menu and pick appropriate AbsMag values from there. Let Celestia calculate their AppMag values. That way you could place them at a different distance and not have to worry about making other changes to the catalog.

The keyword Star is the default in STC catalogs, so it really isn't necessary, but it helps the human reader to keep track. e.g.

Code: Select all

Star "Sekgnai A"  {...}

Your system looks reasonable to me, but I'm no expert in such things.

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Sekgnai.stc file help

Sekgnai.stc file help