Earth's blue vs. lavender atmosphere

[Guest]

Hi everyone:

For some time, I have had a pet "peeve" regarding the Celestia default download. The atmosphere of Earth is lavender colored. I know that there has been prior discussion about it on the forum, but frankly, it just is not correct. From an angle, Earth's atmosphere is a distinct blue.

Here are three photos taken from the Shuttle or ISS of the atmosphere, at a clear angle. As you can see, the atmosphere is blue. I do not see a purposeful tint in the photos to color everything blue. I believe they are true color.

The next image is Celestia's default atmosphere. It is distinctly lavender. There is no trace of blue, until you get close to the ground. Then the sky does change to a blue color. Unless I'm color blind, the Celestia atmosphere is simply tinted the wrong shade.

The last image is the Celestia atmosphere changed to what I feel is the correct blue tint.

I don't know, call me crazy, but what do you all think? If you agree that the atmosphere should be the tint I've adjusted it to, here is the ssc adjustments.

Lower [ 0.3 0.60 0.90 ] # recolored to reflect true blues of atmosphere
Upper [ 0.3 0.5 0.90]
Sky [ 0.3 0.65 0.90 ]

By the way, there appears to be a slight bug in 1.3.0, as evident in the last two images. When I take a screenshot, I save the image OK but its broken into a kind of residual multiview, even though I have not used Multiview. I have to hit the Esc key and Ctrl+D several times before I get a clear single panel screenshot.

Interested in your opinions.

Frank

[JackHiggins]

I agree that the atmosphere in Celestia isnt the same blue as in the photos, but I think your new blue is too exaggerated compared to the surface of the earth.
In celestia the surface doesnt get "bluer" the further away you look, so there is a sudden boundary which looks very unrealistic. However, until this could be changed, the standard celestia blue looks better next to the surface, and not so severe compared to your colouring.

If the atmosphere in celestia could be made to look gradually bluer, your colours would be perfect, but for the moment it's probably better to stick with the standard colour!!

Good idea though!

[bh]

Ahh...here we go again.

bh.

[fsgregs]

OK Jack, I agree that at least in the screenshot, the blue in my ssc seems a bit deep. I want to fade it down so it is paler near the surface. How exactly do you reduce the depth of color in atmospheric tint (as opposed to the shade of color)?

Frank

[Rassilon]

Try

Lower [ 0.30 0.45 0.65 ]
Upper [ 0.30 0.30 0.60 ]
Sky [ 0.35 0.50 0.90 ]

[Guest]

Thanks Rassilon for the guidance. I tweaked the values (for over an hour) and think I've got it!

First, here is the default atmosphere that currently comes with Celestia, taken at three different altitudes (ground, 25 km and 55 km):







Please note that this is full daylight, not twilight. Note the reddish tint in all 3 images.

Here are the same locations with a revised atmosphere tint








The code for the revised set is:

Lower 0.30 0.50 0.65
Upper 0.30 0.45 0.83
Sky 0.30 0.45 0.82

Based on photos of Earth's atmosphere from different elevations, this second set appears correct. If it still needs tweaking, OK lets' tweak it, but honestly, the default atmosphere is lavender. It is NOT how Earth's atmosphere is colored and in my humble opinion, we should replace it if we want Celestia to be accurate.

What do you think?

Frank

[Rassilon]

When I went out today it was clear and bright...One thing I notce about the atmosphere is the lower sky is less saturated and brighter than the upper sky...but I suppose its a matter of perspective...

[fsgregs]

Rassilon:

I agree with you. The layer next to the ground should be whiter and less colored than upper layers. In Celestia, it appears that the Lower Layer is the layer next to the ground, with the Sky second, then the upper layer. As such, the Lower layer should have tint values less than the sky or upper layer, which is what both your code and my minor revision does.

I have been working yet more (what a way to spend a Sunday) on this. Try:

Upper [ 0.26 0.47 0.84 ]
Sky [ 0.30 0.48 0.82 ]
Lower [ 0.30 0.52 0.65 ]

Please notice that I've arranged the code to represent layers from the top down. I toned down the transition from the lower layer to the sky layer so that they blend more smoothly as one goes up.

I positioned myself on the ground, then began to tilt my nose up and flew with the spaceship upward at about 1 km/s until space. The transition appears smooth, the colors begin as a pale sky blue and become deeper as you go up and then fade to black. I've compared them to photos of the sky and they look accurate.

Tell me what you think.

Frank

[Rassilon]

Looks perfect to me Frank...

[JackHiggins]

Brilliant!

[ANDREA]

I have been working yet more (what a way to spend a Sunday) on this. Try:
Upper [ 0.26 0.47 0.84 ]
Sky [ 0.30 0.48 0.82 ]
Lower [ 0.30 0.52 0.65 ]
Tell me what you think.
Frank

Frank. it gives an absolutely realistic vision of our atmosphere, my compliments.
Andrea