Celestia Forums

Amalthea in 1.2.4 looks better then...
...it does in NASA Eyes.

The sad thing is that it's true. NASA should really start using better representations of small bodies.

Yeah.

I think this is fine in this year old thread, if not a mod can split it...

What's the correct color for Amalthea? It appears red in Voyager images, it's red in Celestia Origin as well as default Celestia, but in Project Echoes it's gray.

When I created this it was to point out an inaccuracy of NASA's Eyes.

Anthony_B_Russo10 wrote:When I created this it was to point out an inaccuracy of NASA's Eyes.

The thread's title is "Amalthea", not "Inaccuracies in NASA Eyes". My intent was to continue discussion about the appearance of Amalthea. Compare FarGetaNik's post here. As I said, if my post really shouldn't be here, a mod can split it.

I think replying to a year old thread about the appearance of Amalthea with a question about the appearance of Amalthea is very different from replying to a many years old thread about spectral types with "I think neutron stars might be green".

Well, we'll have to see what Lafuente_Astronomy thinks.

SevenSpheres wrote:I think replying to a year old thread about the appearance of Amalthea with a question about the appearance of Amalthea is very different from replying to a many years old thread about spectral types with "I think neutron stars might be green".

In this particular case, you have justification for doing so. The intent is to give out some new and relevant information, and not to well, do something. It's a pass.

SevenSpheres wrote:The thread's title is "Amalthea", not "Inaccuracies in NASA Eyes"

Just because the title says one thing does not mean that the intention should be the same as the title. Maybe out of hurry, he entitled it that way though his intention was to make a comparison between Celestia and NASA Eyes. You should not think of the title very literally.

This should be in "Physics and Astronomy".

Joey P. wrote:This should be in "Physics and Astronomy".

Why? And can anyone answer my question about Amalthea's color?

Amalthea is red; red is the color of old asteroids. And this should be in Physics and Astronomy because it isn't really about Celestia but rather NASA.

Well color images do commonly show Amalthea's color as red.

except spectrum processing puts the color closer to yellow...

Joey P,
Galileo do indeed show Amalthea's color as red but Galileo images were not composed from RGB filters, the highest quality image was composed from OCV filters (orange, cyan, and violet).

Oh...

But in my opinion I would use RGB color filters.

SevenSpheres wrote:And can anyone answer my question about Amalthea's color?

I did some research for Project Echoes on the color of various celestial objects, including Amalthea. Unfortunately, I couldn't find much useable data. Amalthea certainly reflects more red than blue light... but translating that into a color that a human eye would perceive is another question.

This is what i found:


This spectrum only has 2 data points in the visible range, which is hardly sufficient to derive an 3 vector color for red, green and blue. I tried anyways and ended up with a yellowish-brown color, that when blended down to Amaltheas dark surface, appears almost grey to the human eye. So the answer is: Amalthea is brownish but appears dark grey. If anyone has a more detailed spectrum of Amalthea in the visible range I'd love to see and improve my color rendition for Amalthea.

Askaniy provided me with a list of color indices which lists a value for Amalthea of B-V = 1.5 which is comparable with some of the more red TNO, but since I can't find a value for V-R we can't tell if Amalthea is yellowish or reddish. One source compared Amaltheas color slope with that of Io and stated it was less red than Mars.

So P-type asteroids are slightly green and C-type asteroids slightly blue but dark, right?

Joey P., the green and blue regions in the graph above only denote where the spectra of those asteroids tend to lie, not the actual colour of the asteroids. For all three asteroid spectral types, they are varying degrees of red (their brightness increases with wavelength). The higher the slope, the redder they are. C-type asteroids appear to be almost grey, having a flat spectrum.