Release: A portrait of our Sun

[Cham]

About the flares velocity :

I don't know what velocity are the real flares, but I'm pretty sure they are fast. Probably not as fast as in our addons, however.

Lets do a rough estimate. The sun has a mass of 1.99 E30 kg. I will not take in consideration any light pressure effect, or "solar wind" effect. Lets say a particle (any mass) is ejected from the sun with a velocity large enough to reach an altitude of, say, Y = 130000 km vertically. It will take some time to rise up, fall and reach the sun again. Kinematics gives the instantaneous position

y(t) = v t - g t^2 /2.

After a time t, we get y = 0, so a time t = 2v/g to come back to the sun. To reach an altitude of y = Y, we need the initial velocity

v = SQRT[ 2 g Y ].

Newton theory of gravity gives

g = GM/R^2,

where R is the sun Radius. So the total time of flight is

t = 2v/g = SQRT[ 8 Y R^2 /GM ]

Inserting all numbers gives t = 1945 sec = 32 minutes.

So I guess the numbers I used in my addon are too short by a factor of about 50.

[rthorvald]

Inserting all numbers gives t = 1375 sec = 22 minutes.
So I guess the numbers I used in my addon are too short by a factor of about 50.

So, should i make the flares move 50 times slower, then...?

-rthorvald

[Cham]

Sorry, I made a little error in the rough calculation above (it's now corrected).

Without any light pressure, wind effect and magnetic fields, a typical particle on the sun may take about 30 minutes to make a full jump (up and down). On the real sun, it's more complicated because of the intense magnetic fields generated by the hot plasma, and most ejected particles are electrically charged. On the real pictures (and movies), the trajectories are more circular than parabolic, which shows that magnetic fields are more important here than gravity.

So our addons are giving not enough time by a factor of about 10 to 100 (roughly). To be more realistic, I guess all our RotationPeriods should be divided by that factor (anything between 10 and 100). I suggest 10, so the movements may be visible.

[rthorvald]

To be more realistic, I guess all our RotationPeriods should be divided by that factor (anything between 10 and 100). I suggest 10, so the movements may be visible.

Ok, thank you, very much!
I??ll make a revision tomorrow, and post it here (it??s 2AM here now, have to sleep...).

-rthorvald

[Don. Edwards]

Well I have adapted this solar add-on to work in my HD 28185 system add-on. It works very well in the system.

Thanks for this excelent add-on.

Don. Edwards

[rthorvald]

Well I have adapted this solar add-on to work in my HD 28185 system add-on

I??m glad you could use it! Is the release anywhere on the horizon?

-rthorvald

[rthorvald]

a typical particle on the sun may take about 30 minutes to make a full jump [...] So our addons are giving not enough time by a factor of about 10 to 100 (roughly)

I have updated the SSC file to reflect this. The flares now move with more realistic speeds.
(If anyone likes to see them differently, just edit the _flare rotationperiods).

Here??s the entire Sun SSC file, with new values:

"Sun" "Sol"
{
Texture "th_sun.*"
Emissive true
Radius 709100 #celestia Sol : 695705.371
Oblateness 0.009

EllipticalOrbit {
Period 1e10
SemiMajorAxis 1e-10
Eccentricity 0.00
Inclination 0.00
}

Atmosphere {
Height 1925410
Lower [ 0.9 0.70 0 ]
Upper [ 0.62 0.5 0 ]
Sky [ 0.9 0.65 0 ]
CloudHeight 600
CloudSpeed 1015
CloudMap "th_suncover.*"
}

# RotationPeriod : the actual rotation rate varies with
# latitude L as: ( 14.37 - 2.33 sin2 L - 1.56 sin4 L ) deg/day

RotationPeriod 609.6 # 601.25h @0 deg or 609.6h @16 deg lat
Obliquity 7.25
EquatorAscendingNode 75.62
InfoURL "http://www.thorvaldsen.net/celestia/"
}





Location "Sunspot" "Sol/Sun"
{
LongLat [ 3.1 -1.1 500 ]
Importance 50000
Type "XX"
Size 1000
}





"_sunflare1" "Sol"
{
Mesh "th_placeholder.3ds"
Radius 250000
Emissive true
Oblateness 0.5

EllipticalOrbit
{
Period 9E10
SemiMajorAxis 0.00383
Inclination 90
MeanAnomaly 90
}

Atmosphere {
Height 0
CloudHeight 10
CloudSpeed 100
CloudMap "th_sunflare1.png"
}

RotationPeriod 0.109
Obliquity 45
}



"_sunflare2" "Sol"
{
Mesh "th_placeholder.3ds"
Radius 280000
Emissive true
Oblateness 0.4

EllipticalOrbit
{
Period 9E10
SemiMajorAxis 0.003599
Inclination 180
MeanAnomaly 90
}


Atmosphere {
Height 0
CloudHeight 100
CloudSpeed 100
CloudMap "th_sunflare2.png"
}

RotationPeriod 0.1092
Obliquity 25
}









"_sunflare3" "Sol"
{
Mesh "th_placeholder.3ds"
Radius 210000
Emissive true
Oblateness 0.4

EllipticalOrbit
{
Period 9E10
SemiMajorAxis 0.0041
Inclination 0
AscendingNode 90
MeanAnomaly 45
}


Atmosphere {
Height 0
CloudHeight 100
CloudSpeed 0
CloudMap "th_sunflare3.png"
}

RotationPeriod 0.1075
Obliquity 225
}






"_sunflare4" "Sol"
{
Mesh "th_placeholder.3ds"
Radius 180000
Emissive true
Oblateness 0.7

EllipticalOrbit
{
Period 9E10
SemiMajorAxis 0.0045
Inclination 25
}

Atmosphere {
Height 0
CloudHeight 70
CloudSpeed 100
CloudMap "th_sunflare4.png"
}

RotationPeriod -0.1095
Obliquity 90
}






"_sunflare5" "Sol"
{
Mesh "th_placeholder.3ds"
Radius 250000
Emissive true
Oblateness 0.2

EllipticalOrbit
{
Period 9E10
SemiMajorAxis 0.0044
Inclination 90
MeanAnomaly 90
}

Atmosphere {
Height 0
CloudHeight 100
CloudSpeed 0 #111000
CloudMap "th_sunflare5.png"
}

RotationPeriod 0.107
Obliquity 45
}

... I??ll put the update up on my site soon, too.
-rthorvald

[Buzz]

Very nice rthorvald! A question though: will you also make a lo-res version available? If you only include the levels up to level 2, it will be "real" too!

Buzz

[rthorvald]

will you also make a lo-res version available? If you only include the levels up to level 2, it will be "real"

I??m afraid that ditching the higher levels will only save about 30MB, so the download would still be more than 100MB.

The Addon contains lores and medres as it is.
I decided against making a separate "light" version, since fsgregs already has a very nice 2k Sun up on the Motherlode, and a scaled down version of my own would not differ very much from that one.

-rthorvald

[danielj]

So level 2 is a 4k texture for the Sun?Is that right?
I don??t entirely agree that only until level 2,there are real things.Maybe level 3 as well is realistic or at least mostly realistic.What do you think?I know there are closeups of sunspots specially by some probes like SOHO.For example here:
http://www.tretipol.cz/img/pic/9/sunspots.jpg
Other thing,the faculae should be visible in Sun??s texture as well.Look for this bright regions:
http://www.astro.su.se/~alexis/images/SunSpot.jpg
Look to this very detailed sunspot
http://www.physast.uga.edu/~rls/1020/ch7/Image_of_sunspots.jpg
And probably the best ever view of the susnpots:
http://www.solarphysics.kva.se/NatureNo ... color.jpeg
But even so,looking to real photos,I can say the result is very good and realistic.Congratulations!


[[/url]

[Buzz]

OK rthorvald, I see your point. I *will* find a way to get it!

[Frank Hunter]

Hi rthorvald,

Thank you for the terrific sun replacement . The flares are superb. I have only just installed it and unfortunately found a flaw in the presentation. There is a rectangle of lighter grey, the size depends on the distance from the sun. I made a screen shot of it but it, and the sun wouldn't copy, just the black background. I also made a Cel://URL which I thought might be used to diagnose the problem.

cel://Freeflight/2005-01-09T05:33:26.03 ... 40599&lm=6

I run a G5 iMac, the graphics card is Nvidia GeForce FX 5200, 64 MB VRAM. The rest: 1GB RAM /18ghz/OSX 10.3.7.

This is in no way a slight on a great addon, I just thought you would want to know about it.

Regards,
Frank H.

[Frank Hunter]

Hi again rthorvald,

I used a different method to make a screenshot and now everything shows. I don't know how to insert it into this message. I notice that when viewing the screen at different angles, the rectangle will disappear. Maybe a result of the flat screen?

Thanks again
Frank H.

[rthorvald]

I used a different method to make a screenshot and now everything shows. I don't know how to insert it into this message. I notice that when viewing the screen at different angles, the rectangle will disappear.

I need the screenshot to understand what you are seeing.
To insert it into a message, do this:
- upload it to a web service - if you have web space with your ISP, use that, if not there are several free hosting services you can use. Someone has made a list of these in the User??s Forum.
- Use the "Img" function in the board editor, and insert the URL of your uploaded image there.

-rthorvald

[Frank Hunter]

rthorvald wrote
I need the screenshot to understand what you are seeing.

[/img]http://img53.exs.cx/img53/1783/fromclipboard8ti.png

Frank Hunter

[rthorvald]

rthorvald wrote
I need the screenshot to understand what you are seeing.

I don??t think this has anything to do with the Sun addon. I tested your CelUrl right now on an imac with exactly the same specs you have, and i don??t see this.
It looks like your flare.jpg file is missing, does not load, or is badly made. Check in your /celestiaresources/textures/ to see what you have there; look for a file named "flare.jpg".

-rthorvald

PS: there are a number of alternate flares floating around here on the forums; i expecially like Don. Edward??s one, in this thread:
http://shatters.net/forum/viewtopic.php?t=4712
Also, Cham has made some that looks more "natural", here:
http://shatters.net/forum/viewtopic.php?t=6467

[HJS]

I downloaded the Sol/Sun add-on some days ago and I think that its a wonderful addition to Celestia. I seemed to be having some difficulty seeing the flares, however. Sometimes they would work and sometimes they wouldn't. I finally sat down to analyze the situation and discovered that Celestia considers the flares to be "clouds." Therefore if you have turned off "clouds" the flares will not appear. Please keep this in mind when viewing the Sol/Sun with the new add-on.

[Vincent]

First, a big thanks for this wonderful addon !!

I want to convert all png files into dds format. Do I have to convert them in DXT1 format (without alpha layer) or in DXT3 (with alpha layer). In DXT1, the files would be nearly 500 Ko each and in DXT3, it's the double. So can you tell me if your files needs analpha layer...

Thanks again

@+
Vincent

[rthorvald]

I want to convert all png files into dds format. [...] So can you tell me if your files needs analpha layer...

The Suncover and Sunflare files needs alpha layers, but not the th_sun texture itself.
However, i expect you will lose some quality in the conversion. If you get an acceptable result, i??d be very interested to see it.

-rthorvald

[Vincent]

Thanks ! I'll let you know if the result is worth it !

@+
Vincent