Celestia Forums

When you select the Sun (Sol), you can't use the "Sync Orbit" Feature!
The "lock" key doesn't work either, nor the "chase" key.
Is there a work around for the Sync option ?

Second question:
Is it possible to change the sun parameters (rotation period) ?

Paul,

This does indeed seem to be a limitation in Celestia.

However, a workaround might be to use an SSC file to define a "planet" that has a mimimal orbital radius and maximal orbital period and a diameter a slight bit more than the sun's (so you can apply and see an appropriate surface texture) but with the appropriate rotational period. Then you can sync to that.

Selden,
thanks for the idea. It works well.
The only thing is to have the rotation axis tilted in the same direction as the sun. I know its 7.25deg, but I'm having difficulties to get the correct EquatorAscendingNode parameter.

Paul,

I'm not sure how to translate it into "fake planet" coordinates, but
http://sohowww.nascom.nasa.gov/data/ancillary/ claims
"the longitude of the ascending node of the solar equator as 75.62 and the position of the pole of the solar equator in celestial coordinates as 286.11 right ascension and 63.85 declination. This definition is consistent with a solar rotation axis determined from the Carrington elements for a date of 1 January 1990"
but I'm guessing you know this already.

Calculus wrote:When you select the Sun (Sol), you can't use the "Sync Orbit" Feature!
The "lock" key doesn't work either, nor the "chase" key.
Is there a work around for the Sync option ?

Second question:
Is it possible to change the sun parameters (rotation period) ?

I'll fix the limitations with sync orbit, lock, and chase in 1.2.6 . . .

It's not currently possible to change the sun parameters without modifying the code. All stars have the same rotation rate, because I've tried to keep the per-star data as compact as possible.

--Chris

selden wrote:"the longitude of the ascending node of the solar equator as 75.62 and the position of the pole of the solar equator in celestial coordinates as 286.11 right ascension and 63.85 declination. This definition is consistent with a solar rotation axis determined from the Carrington elements for a date of 1 January 1990"
but I'm guessing you know this already.

When I look in Celestia I found for the sun axis about 270ra and 64 declination. Strangely, when I don't enter any parameter for the fake planet, it works. (I don't know where are the 7.25 Obliquity!!!). Mayby Grant could explain that!

For those interested, here is my fake sun:
"Sun" "Sol"
{
Radius 696000 #celestia 695705.371
EllipticalOrbit {
Period 1e10
SemiMajorAxis 0.000000001
Eccentricity 0.000
Inclination 0.00
}

RotationPeriod 609.6 # 601.25 @0 deg / 609.6h @16 deg lat
Obliquity 0.0 #7.25
#LongOfRotationAxis
#EquatorAscendingNode
}

Calculus wrote:Strangely, when I don't enter any parameter for the fake planet, it works. (I don't know where are the 7.25 Obliquity!!!). Mayby Grant could explain that!

With the Mark I Eyeball, I'd say that this is because the Sun's equator is not inclined relative to the ecliptic in Celestia!
(The RA and dec Selden gives translate to an Obliquity of 7.25 and an EquatorAscendingNode of 75.61, but to my eye the Celestia Sun rotates with its equator parallel to the ecliptic.)

Grant

Thanks Grant,
I'm going to change my fake sun, and in fact it'll be the actual one with the correct parameters!!