I have a problem with celestia

[PlutonianEmpire]

the problem is the lighting from multiple nearby stars on a planet.

One is a bright blue B star, while the other is a M3V dwarf star.

the planet is orbiting the smaller dwarf star. and in the planet's sky in certain parts of orbit, both stars appear the same size.





Personally, I think that since the planet is so close to both stars, the surface should be BRIGHTLY lit by both stars, and not just brightly lit by one star and dimly lit by the other.

[symaski62]

Ctrl + V => OpenGL 2.0

[Hamiltonian]

The surface of a red dwarf is dimmer than the surface of a B star. So the red dwarf would need to be much larger in the sky to shed the same light as the B star.
Maybe Celestia is causing confusion by showing both stars with equal surface brightnesses. II guess there's a limit to how much brighter or dimmer a surface texture can usefully be made.

[PlutonianEmpire]

Ctrl + V => OpenGL 2.0

I tried that, it didn't work.

[Malenfant]

can you show us the SSC code to try this ourselves? It may be something to do with the bugs still in the multiple lighting implementation

[PlutonianEmpire]

Code: Select all

Star "Vulcana" {
   SpectralType "M3V"
   AbsMag 10.500

   OrbitBarycenter "HD 158186"

   EllipticalOrbit {
      Period             0.2085
      SemiMajorAxis      1.000
      Eccentricity       0.000
      Inclination        0.000
      AscendingNode      0.000
      ArgOfPericenter    0.000
      LongitudeNode      0.000
   }
}

Code: Select all

"Volcanica" "Vulcana" {
   Texture "gc_vulca_03.jpg"
   BumpMap "gc_vulca_03-bump.jpg"
   BumpHeight  1.7
   NightTexture "gc_vulca_03-night.jpg"
   Radius 5610.000
   Oblateness  0.180
   Color [ 0.14 0.72 0.19 ]
   BlendTexture true

   Atmosphere {
      Height 56.100
      Lower [ 0.36 0.14 0.04 ]
      Upper [ 0.20 0.41 0.52 ]
      Sky [ 0.29 0.28 0.71 ]
      CloudHeight  5.610
      CloudSpeed  10.000
      CloudMap "gc_gener_05-clouds.png"
   }

   EllipticalOrbit {
      Period            0.6758
      SemiMajorAxis     0.018283870967741935483870967741935
      Eccentricity      0.0000
      Inclination       0.0000
      MeanAnomaly       168.3022
   }

   Obliquity                0.000

   Albedo           0.16
}

[Malenfant]

Do you get any lighting at all from the other star?

I'm wondering if you need to have both stars orbiting a barycentre and defined in the SSC, not just one (and the other defined in an STC)?

[PlutonianEmpire]

Do you get any lighting at all from the other star?

I'm wondering if you need to have both stars orbiting a barycentre and defined in the SSC, not just one (and the other defined in an STC)?

Yes, but the only lighting I saw off the dimmer star I saw reflecting off the planet's clouds. It is difficult to see the lighting from the smaller star unless you turn off all the lights in the room.

[ajtribick]

Out of interest, what are the apparent magnitudes of the two stars from the planet?

EDIT:

Set up this system myself (required editing of starnames.dat, apparently 1.4.0pre6 doesn't recognise catalogue references in the OrbitBarycenter field, perhaps I should upgrade), the red dwarf is at apparent magnitude -29.74, the blue star is a magnitude -38.08, which means that the blue star appears to be over 2000 times brighter.

Not surprising that the red dwarf isn't providing much illumination.

[Malenfant]

PE - have you posted EVERYTHING (ie SSCs and STCs) that your system uses here? You've got a barycentre defined but where's the other B V star? IIRC the Barycentre should replace HD 158186 and the stars should be defined in the STC shouldn't they? Like this (from Fridger's Binary Stars addon):

Code: Select all

Barycenter "HIP7372"
{
RA        23.753985
Dec      -29.910568
Distance  77.126269
}


7372 "HIP7372 A" # component A
{
OrbitBarycenter "HIP7372"
SpectralType "K3V"
AppMag  7.94

        EllipticalOrbit {
                Period               4.561
                SemiMajorAxis        2.582 # mass ratio 0.74 : 1.71
                Eccentricity         0.330
                Inclination         58.204
                AscendingNode      252.696
                ArgOfPericenter     56.802
                MeanAnomaly        282.491
        }
}

"HIP7372 B" # component B
{
OrbitBarycenter "HIP7372"
SpectralType "G2V"
AppMag 8.12

        EllipticalOrbit {
                Period               4.561
                SemiMajorAxis        1.123 # mass ratio 0.74 : 1.71
                Eccentricity         0.330
                Inclination         58.204
                AscendingNode      252.696
                ArgOfPericenter    236.802
                MeanAnomaly        282.491
        }
}


And then the planets should be placed in the SSC...

[PlutonianEmpire]

Out of interest, what are the apparent magnitudes of the two stars from the planet?

From the planet, the apparent magnitude of the smaller, dimmer star is -30.

[PlutonianEmpire]

PE - have you posted EVERYTHING (ie SSCs and STCs) that your system uses here?

The main B star is a real life star, HD 158186, so the B star IS the barycenter. The hip number is 85569.

[Malenfant]

The main B star is a real life star, HD 158186, so the B star IS the barycenter. The hip number is 85569.

Yes, but you have to explicitly define it as such still.

85569 is at RA 17 29 12.925, Dec -31 32 03.44 and has a parallax of 0.0002 arcesconds, which means it's 16,300 ly away (how does that even render in Celestia?)

Code: Select all

Barycenter "HIP85569"
{
RA        262.3038514
Dec      -31.53428573
Distance  16308
}


85569 "HIP 85569 A" # component A
{
OrbitBarycenter "HIP85569"
SpectralType "B2II"
AbsMag  -6.5

EllipticalOrbit {
       Period               0.000001
       SemiMajorAxis        0.000001
       Eccentricity         0
       Inclination       0
       AscendingNode        0
       ArgOfPericenter      0
       MeanAnomaly          0
        }
}

"HIP 85569 B" # component B
{
OrbitBarycenter "HIP85569"
SpectralType "M3V"
AbsMag  10.5

EllipticalOrbit {
      Period             0.2085
      SemiMajorAxis      1.000
      Eccentricity       0.000
      Inclination        0.000
      AscendingNode      0.000
      ArgOfPericenter    0.000
      LongitudeNode      0.000
   }
}


This should work (EDIT: solved the problem I was having with it)

BTW, I copied the Appmag from your code, PE - you sure that's right? Seems rather bright for an M dwarf 16,000 lightyears away. You sure that's not the AbsMag?

[PlutonianEmpire]

You accidentally made it an AppMag somehow. It's supposed to be an AbsMag (for the dwarf).

[Malenfant]

the AbsMag is 10.5, not appmag.

So it is, I misread I changed my code now to use AbsMags

EDIT: Never mind, problem solved.

[PlutonianEmpire]

try copying an existing STC file (one that DOES work), and overwrite the existing code with the code you want to implement. that may work.

[Malenfant]

try copying an existing STC file (one that DOES work), and overwrite the existing code with the code you want to implement. that may work.

That's exactly what I did. That's why I'm a bit mystified that this doesn't work...

EDIT: Dammit! That's why it didn't work, the stupid text editor decided to suddenly switch directories that it was saving files into for no apparent reason (and I didn't check that at first). So it wasn't saving in my extras directory, which meant Celestia couldn't see it.

This code should work.

Code: Select all

Barycenter "HIP85569"
{
RA        262.3038514
Dec      -31.53428573
Distance  16308
}


85569 "HIP 85569 A" # component A
{
OrbitBarycenter "HIP85569"
SpectralType "B2II"
AbsMag  -6.5

EllipticalOrbit {
       Period               0.000001
       SemiMajorAxis        0.000001
       Eccentricity         0
       Inclination       0
       AscendingNode        0
       ArgOfPericenter      0
       MeanAnomaly          0
        }
}

"HIP 85569 B" # component B
{
OrbitBarycenter "HIP85569"
SpectralType "M3V"
AbsMag  10.5

EllipticalOrbit {
      Period             0.2085
      SemiMajorAxis      1.000
      Eccentricity       0.000
      Inclination        0.000
      AscendingNode      0.000
      ArgOfPericenter    0.000
      LongitudeNode      0.000
   }
}


Note that you MUST have a non-zero value for the period and semimajor axis of A around the barycenter, otherwise it renders as nonsense.

Oddly enough though, if I type HIP 85569 into the text entry window in Celestia pre7, it doesn't select the barycenter itself, it automatically selects the A star.


So, stick your planet around that and see what happens.

[PlutonianEmpire]

I'm thinking its because the star doesn't have a "proper" name. I entered a name for this star in the starnames.dat file, and then set the orbitbarycenter thing to say the name of the star instead of the number, and that's how it works on my system.

[Malenfant]

I'm thinking its because the star doesn't have a "proper" name. I entered a name for this star in the starnames.dat file, and then set the orbitbarycenter thing to say the name of the star instead of the number, and that's how it works on my system.

AFAIK (someone correct me if I'm wrong?) if you're replacing a star that already exists in stars.dat (85569 is one of those) then you need that HIP number in there next to the name of the A star, like this:

Code: Select all

85569 "HIP 85569 A" # component A

You can put anything you like in the quotes, but that HIP number outside the quotes has to be there.

[PlutonianEmpire]

I'm not "replacing" it, per se. I never edited ANYTHING out of the RL star. I simply put a fake star in orbit around the RL star.

The stc code I posted earlier was the ENTIRE stc that I had in the extras folder. I did not alter HD 158186 at all.

Interestingly, when I replaced the name i gave to HD 158186 with the hip number instead, the companion i created disappeared, so you're not the only one encountering problems with numbers, it seems.