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Main
Date: 29 Aug 2006 17:39:23
From:
Subject: palette or chart of star colors ?
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Hi,
To create renderings of stars I need to know their spectral color to
represent them the best I can using a calibrated screen.
For example, I try to render Pollux and its exoplanet.
http://www.astrosurf.org/lombry/alienworlds-renderings.htm (close to mid of
page, left)
This bright star is a K0III, thus orangeous.
But a K5 or K7 star is also "orangeous" but with redder.
So how to know what is the exact tint or palette to use to render exactly a
K0III star (and tens of others) ?
NB. Of course nobody will never tell me that my Pollux is G6 instead of K0
on his creen, but better to render them correctly ;-)
Is there somewhere on the web something that could help me to pick up the
exact color of each spectral class ?
No color palettes includes in office applications uses such a system (but
rather CMY, RGB, etc). So how to proceed ?
I think to a high resolution true color H-R diagram, maybe, but where could
I find such a chart in hires, and online ?
Or isn't there an astronomy application that shows them all correctly (I
think to Starry Night Pro 6 as I'm going to buy it) or even a small freeware
dedicated to stars ?
Do you have another idea to check spectral colors electronically (and if
possible with all intermediate stages, G0, G3, G7...)
Thanks in advance
Thierry
http://www.astrosurf.org/lombry/
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Date: 29 Aug 2006 11:19:50
From: William Hamblen
Subject: Re: palette or chart of star colors ?
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On Tue, 29 Aug 2006 17:39:23 +0200, <Thierry > wrote:
>Is there somewhere on the web something that could help me to pick up the
>exact color of each spectral class ?
Stars are almost black bodies, so you could use the Planck energy
distribution formula to calculate the energy emitted at visual
wavelengths. You also can look up spectra in reference books. It
might be easier to create a tint based on color temperature
corrections in graphics arts software, each spectral class having a
characteristic surface temperature:
Class Temperature Star color
O 30,000 - 60,000 K Bluish ("blue")
B 10,000 - 30,000 K Bluish-white ("blue-white")
A 7,500 - 10,000 K White with bluish tinge ("white")
F 6,000 - 7,500 K White ("yellow-white")
G 5,000 - 6,000 K Light yellow ("yellow")
K 3,500 - 5,000 K Light orange ("orange")
M 2,000 - 3,500 K Reddish orange ("red")
The tints of real stars are very unsaturated and you would want to
exaggerate the colors to get a good appearance. An ordinary
incandescent lamp filament at 2,900 K is similar in temperature to a
class M star and appears "white" to most eyes.
Bud
--
The night is just the shadow of the Earth.
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Date: 30 Aug 2006 22:02:40
From:
Subject: Re: palette or chart of star colors ?
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"William Hamblen" <wrhamblen@comcast.net > wrote in message
news:e0p8f21dvg26hjqlgneb7l0i5jtm1n67is@4ax.com...
> On Tue, 29 Aug 2006 17:39:23 +0200, <Thierry> wrote:
>
>>Is there somewhere on the web something that could help me to pick up the
>>exact color of each spectral class ?
>
> Stars are almost black bodies, so you could use the Planck energy
> distribution formula to calculate the energy emitted at visual
> wavelengths. You also can look up spectra in reference books. It
> might be easier to create a tint based on color temperature
> corrections in graphics arts software, each spectral class having a
> characteristic surface temperature:
>
> Class Temperature Star color
> O 30,000 - 60,000 K Bluish ("blue")
> B 10,000 - 30,000 K Bluish-white ("blue-white")
> A 7,500 - 10,000 K White with bluish tinge ("white")
> F 6,000 - 7,500 K White ("yellow-white")
> G 5,000 - 6,000 K Light yellow ("yellow")
> K 3,500 - 5,000 K Light orange ("orange")
> M 2,000 - 3,500 K Reddish orange ("red")
>
Hi,
What I need is a way to compute a high resolution version of this graph
(title "la couleur des étoiles", the color of stars)
http://www.astrosurf.org/lombry/vie-etoiles.htm
to know for example that 14000 K is B7 I, and conversely, etc
Maybe using a formula ?
Thierry
> The tints of real stars are very unsaturated and you would want to
> exaggerate the colors to get a good appearance. An ordinary
> incandescent lamp filament at 2,900 K is similar in temperature to a
> class M star and appears "white" to most eyes.
>
> Bud
> --
> The night is just the shadow of the Earth.
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Date: 31 Aug 2006 09:18:18
From: Ernie Wright
Subject: Re: palette or chart of star colors ?
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Thierry wrote:
> What I need is a way to compute a high resolution version of this graph
> (title "la couleur des étoiles", the color of stars)
> http://www.astrosurf.org/lombry/vie-etoiles.htm
> to know for example that 14000 K is B7 I, and conversely, etc
> Maybe using a formula ?
I've found that it's much easier to use the B-V color index, rather than
the spectral class. Harwit gives the formula
T = 7300 / ( bv + 0.73 )
where T is color temperature and bv is the B-V index. (There are other
formulas that give slightly different answers.) You can then use a
table like
http://www.vendian.org/mncharity/dir3/blackbody/
or a program like
http://www.fourmilab.ch/documents/specrend/
to relate color temperature to an RGB value.
- Ernie http://home.comcast.net/~erniew
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Date: 29 Aug 2006 16:16:39
From: Chris L Peterson
Subject: Re: palette or chart of star colors ?
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On Tue, 29 Aug 2006 17:39:23 +0200, <Thierry > wrote:
>To create renderings of stars I need to know their spectral color to
>represent them the best I can using a calibrated screen.
Try this:
http://hubblesource.stsci.edu/sources/toolbox/entry/color_swatch/
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 29 Aug 2006 21:01:00
From:
Subject: Re: palette or chart of star colors ?
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"Chris L Peterson" <clp@alumni.caltech.edu > wrote in message
news:51q8f2hussjnb39rnajc7iqguntguf7mbo@4ax.com...
> On Tue, 29 Aug 2006 17:39:23 +0200, <Thierry> wrote:
>
>>To create renderings of stars I need to know their spectral color to
>>represent them the best I can using a calibrated screen.
>
> Try this:
> http://hubblesource.stsci.edu/sources/toolbox/entry/color_swatch/
>
>
Yes Chris ! (at least it looks fine, I will try, all the more I use
Photoshop ;-))
Thanks
Thierry
_________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
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