APOD: NGC 1360: The Robin's Egg Nebula (2023 Aug 05)

[Ann]

Gimp is a free image processing and manipulation program available for Windows, Mac and Linux:

Huh. I'd need someone to help me install it, and then someone to show me how to use it. Primarily for finding out about the exact color of an image, or more likely, of parts of an image.

Don't know if I can do that, so is it okay if I ask you again, Johnny?

Ann

Does this work for you - https://www.colorcodepicker.com ? You just upload an image and you can then move your mouse over it and it displays the RGB values.

Wow! That seems very helpful, indeed. Of course, there is still the hex code...

Ann

[Chris Peterson]

neither the Robin's Egg Nebula nor a robin's egg have a colour hue or a wavelength.
Both look like some indigo ink that thickens white to pale cyan to blue to dark violet to black.

The egg shell has a pretty uniform hue. The image of the egg does not because of the intensity variations. Even with a hue created by a very narrow wavelength, there is no single color (or meaningful RGB representation) because the actual color is defined by intensity as well as hue.

here's a fragment of the pic of a robin's egg
Robin's Egg-.jpg
You can see that a point of the sun's reflection is white; here the random movement of a photon scattered by CaCO₂ crystallites is minimal and chances for an ink molecule to absorb that photon is minimal.
The wider the angle from the sun's reflection the greater is the distance a typical photon travels through the egg's shell material before coming out along your line of sight. That is exactly what thickening a dye means.

There's a limit to that thickening here: a robin's egg has a thin shell with a budget quantity of ink and just white matter beneath.
So the longest travellers among photons get to pass through the shell and scatter from the white.
You can see just white to pale cyan to cyan-blue, no blue to dark violet to black

The hue is uniform. You're referring to a geometric effect.

[johnnydeep]

Huh. I'd need someone to help me install it, and then someone to show me how to use it. Primarily for finding out about the exact color of an image, or more likely, of parts of an image.

Don't know if I can do that, so is it okay if I ask you again, Johnny?

Ann

Does this work for you - https://www.colorcodepicker.com ? You just upload an image and you can then move your mouse over it and it displays the RGB values.

Wow! That seems very helpful, indeed. Of course, there is still the hex code...

Ann

The hex code is there as well, or else I'm not understanding what you mean:

[Ann]

Does this work for you - https://www.colorcodepicker.com ? You just upload an image and you can then move your mouse over it and it displays the RGB values.

Wow! That seems very helpful, indeed. Of course, there is still the hex code...

Ann

The hex code is there as well, or else I'm not understanding what you mean:


colorcodepicker website example.jpg

Oh yes, it's there! It was very careless of me to miss it.

Ann

[VictorBorun]

The egg shell has a pretty uniform hue. The image of the egg does not because of the intensity variations. Even with a hue created by a very narrow wavelength, there is no single color (or meaningful RGB representation) because the actual color is defined by intensity as well as hue.

here's a fragment of the pic of a robin's egg
Robin's Egg-.jpg
You can see that a point of the sun's reflection is white; here the random movement of a photon scattered by CaCO₂ crystallites is minimal and chances for an ink molecule to absorb that photon is minimal.
The wider the angle from the sun's reflection the greater is the distance a typical photon travels through the egg's shell material before coming out along your line of sight. That is exactly what thickening a dye means.

There's a limit to that thickening here: a robin's egg has a thin shell with a budget quantity of ink and just white matter beneath.
So the longest travellers among photons get to pass through the shell and scatter from the white.
You can see just white to pale cyan to cyan-blue, no blue to dark violet to black

The hue is uniform. You're referring to a geometric effect.

You are right and I was partly wrong.
Here I try to compare two ways to make the picture fragment of the robin's egg more uniform:
1) to adjust the input range of RGB; that's a transformation that keeps the hue
2) to adjust gamma; that's a transformation that keeps the sort of the dye and just makes it thinner or thicker

hue or dye 0.jpg (7.24 KiB) Viewed 2924 times

hue or dye - input range.jpg (8.76 KiB) Viewed 2924 times

hue or dye - gamma.jpg (8.43 KiB) Viewed 2924 times

You can see that both ways are successful and that the hue-preserving one is doing even better, discarding my claim that there is no hue.
There is a hue, and it is cyan, and it is primary.
There are 6 primary hues: red, yellow, green, cyan, violet, pink.
A dye of a primary hue can be thinned or thickened without changing its hue.

I still claim that there is no hue to this APOD cyan nebula: it is a blue (a.k.a. an indigo), not a primary stuff, showing the range of hues cyan to violet.