What the Hubble Palette really does.

[ollypenrice]

This is a good way to spend 5 minutes.

The HP's key feature, its underlying rationale, is that it 'stretches' the colour data contained in OIII, Ha and SII across the full range of visible colour spectrum. As these data arrive from nature, they are compressed into the right hand half of the spectrum, so it goes OIII Ha SII.  

 

This leaves most of green and all of blue, over to the left, unused. All the HP does is move everything to the left. SII  makes the smallest movement into the middle of red. Ha makes the jump from deep red to the middle of green and OIII jumps from the green-blue border to the middle of blue.

Although the HP is not a natural colour palette it does, in this sense, respect nature in not inverting the captured wavelengths. Any wavelength which, at capture, was longer than another at capture will remain longer in the final image - and so with any which was shorter.

Often in amateur AP discussions there seems to be an underlying notion that the Hubble Palette is just a way of colourizing a picture, but that's not so. It has a solid physical foundation. (I still don't like it but that's because I think nature is the greatest painter in the universe...)

Olly

Edited October 9, 2021 by ollypenrice

[StuartT]

Thanks so much for posting this. I think this is the first time I have actually understood this!

[DaveS]

I also found this from Dr Becky

 

[teoria_del_big_bang]

9 hours ago, ollypenrice said:

This is a good way to spend 5 minutes.

The HP's key feature, its underlying rationale, is that it 'stretches' the colour data contained in OIII, Ha and SII across the full range of visible colour spectrum. As these data arrive from nature, they are compressed into the right hand half of the spectrum, so it goes OIII Ha SII.  

 

This leaves most of green and all of blue, over to the left, unused. All the HP does is move everything to the left. SII  makes the smallest movement into the middle of red. Ha makes the jump from deep red to the middle of green and OIII jumps from the green-blue border to the middle of blue.

Although the HP is not a natural colour palette it does, in this sense, respect nature in not inverting the captured wavelengths. Any wavelength which, at capture, was longer than another at capture will remain longer in the final image - and so with any which was shorter.

Often in amateur AP discussions there seems to be an underlying notion that the Hubble Palette is just a way of colourizing a picture, but that's not so. It has a solid physical foundation. (I still don't like it but that's because I think nature is the greatest painter in the universe...)

Olly

Cheers Olly, I really fancied that book but it is a bit pricey. maybe I will have to ask Santa very nicely 🙂 

Steve

[vlaiv]

I just want to point out that there is "anatomically correct" version of spectrum:

And that no color that you see in above spectrum is correct color. No computer (or tablet / smartphone) display is currently capable of rendering true spectrum image.

This "anatomically correct" version is cleverly produced by picking color that computer screen is capable of producing that is visually closest to the true spectral color.

 

[ollypenrice]

50 minutes ago, vlaiv said:

I just want to point out that there is "anatomically correct" version of spectrum:

And that no color that you see in above spectrum is correct color. No computer (or tablet / smartphone) display is currently capable of rendering true spectrum image.

This "anatomically correct" version is cleverly produced by picking color that computer screen is capable of producing that is visually closest to the true spectral color.

 

That's very good, with a proper 'teal blue' for the OIII and a red gamut which I think could distinguish convincingly Ha fom SII.

Olly

Edited October 9, 2021 by ollypenrice

[ollypenrice]

13 hours ago, DaveS said:

I also found this from Dr Becky

 

Very good. Just one thing, though: the nice bit of video graphics allegedly showing the merging of broadband red, green and blue-filtered images produces an image in the Hubble palette rather than in RGB, I would say.

 

A digression on the subject of eyes...  If, while talking to someone, we roll our eyes to one side and back again, with our eyelids open, the eye movement is fairly innocent. If, however, we close our eyelids during the eye movement, open them with our eyes looking away, close them while rolling them back and then open them again, the effect is 'very disturbing' for  the other person. I suspect that Dr Becky knows this... 

Olly

Edited October 10, 2021 by ollypenrice
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