True colour of The Sun?

[MYLUCKYSTARS]

I hear the Sun is white (http://www.universetoday.com/18689/color-of-the-sun/ http://solar-center.stanford.edu/SID/activities/GreenSun.html) This is true right?

If it is white then I think the most annoying thing it that it hardly ever represented as such.

[Knight of Clear Skies]

It is nearly white, but we rarely see it as such. Our atmosphere scatters more blue light than red, so the closer it is to the horizon the redder it appears.

[ollypenrice]

Complicated. Since what we call white light is (to all intents and purposes) sunlight then, yes, the sun gives out white light.

Now, how does that white light get to us? On a clear day the sky is blue. Why? Because the atmosphere has intercepted the short wavelength sunlight (blue light) and sent it scattering around within itself so that it finally makes its way into our eyes from any direction, not directly from the sun's disk. So the sun's disk that we see is the the sun's white light minus all that scattered blue. It is, in effect, shifted towards the red end. The lower the sun is in the sky, the greater the scattering of its short (blue) wavelengths so the redder it looks.

You are annoyed that the sun is not 'represented' as white? But your own eyes don't represent it as white for the reasons outlined above. So far as your eyes are concerned it isn't white, it is 'white minus some blue.'

If you're talking about solar images then 'white light' solar images often are presented as white. They are taken through filters which simply dim the full solar spectrum. They look greyscale to the eye at the eypiece and are usually presented as such. Seen through solar film ot a Hershel wedge the disk looks white and is usually shown as such.

If you're talking about H alpha solar images like this

...then they will have been captured, like this image, in an Ha filtered solarscope. The Ha line is a deep red but the camera is usually monochrome and the colour is artificial. However, the image processor (in this case me) may try to recreate the colour seen through this filter at the eyepiece. At the EP the view is actually redder than this, but I like to shift the colour over to the green end since this accords with a natural view of the sun as seen through an atmospere. This is no more artificial than presenting an Ha image in greyscale because Ha isn't grey, it's red.

Olly

Edit, Apologies to Knight, who is saying the same thing but typing faster!

[Moonshane]

it looks white to me when using a baader film solar filter but then we are not seeing the whole sun I suppose. I think we see straight through the Ha layers?

[Knight of Clear Skies]

Edit, Apologies to Knight, who is saying the same thing but typing faster!

Or possibly just typing less. Thanks for the fuller explanation.

it looks white to me when using a baader film solar filter but then we are not seeing the whole sun I suppose. I think we see straight through the Ha layers?

I'm not totally sure, but I think the light from the chromosphere is simply swamped by the much brighter photosphere. So a little of the Ha emission would go through the Film, but you wouldn't really notice it. (Hope I've got that right.)

[MYLUCKYSTARS]

You are annoyed that the sun is not 'represented' as white? But your own eyes don't represent it as white for the reasons outlined above. So far as your eyes are concerned it isn't white, it is 'white minus some blue.'

If you're talking about solar images then 'white light' solar images often are presented as white. They are taken through filters which simply dim the full solar spectrum. They look greyscale to the eye at the eypiece and are usually presented as such. Seen through solar film ot a Hershel wedge the disk looks white and is usually shown as such.

If you're talking about H alpha solar images like this

...then they will have been captured, like this image, in an Ha filtered solarscope. The Ha line is a deep red but the camera is usually monochrome and the colour is artificial. However, the image processor (in this case me) may try to recreate the colour seen through this filter at the eyepiece. At the EP the view is actually redder than this, but I like to shift the colour over to the green end since this accords with a natural view of the sun as seen through an atmospere. This is no more artificial than presenting an Ha image in greyscale because Ha isn't grey, it's red.

Olly

Edit, Apologies to Knight, who is saying the same thing but typing faster!

That's ok. But what excuse do science documentaries with animations that represent The Sun from space have?

[soundwave]

There is a difference between what is the real color of the sun (regarding wavelengths), and what color we would see if we could look at the sun from space without filters (and not go blind).

From what I understand, the Sun is not hot enough to really be white, although it's pretty close:

From PhysLink.com:

"The Sun's surface temperature (5,500 degrees C) produces a range of visible light (red to blue) in which yellow is the most plentiful, but not much more than other colors it produces."

But our eyes aren't so sensitive to small changes in these amounts, and even if there is a bit of difference in amount of wavelengths, our brain would still interpret sunlight as white.

From Wikipedia:

"White is the color the human eye sees when it senses light which contains all the wavelengths of the visible spectrum. This light stimulates all three types of color sensitive cone cells in the eye in nearly equal amounts."

So the real color of the Sun is almost white

But our brain would say it's really white if we could watch the sun from space and not go blind.

Also, this graph can help illustrate the changes in wavelengths amounts. (the Sun's surface temp is 5800K)

I believe that science documentaries often show the Sun as if filtered with an H-Alpha filter, in order to show convections and all the cool details,

but they usually make sure to mention that sunlight is white, and that it's a combination of all colors of the spectrum.

P.S: I've read somewhere the the "true" color of the sun is #FFF5F2 ... I have no idea if that's based on any math or anything  () haha

[Steve Ward]

I always present my "Whitelight" images in Monochrome as it's a pretty accurate representation of what is visible to the eye through either Baader film or a Wedge.

The only time I concede to the orange orb is when I'm shooting Sunrise/Sunset images in colour ... 

http://www.tuxamito.com/joomla/index.php/en/component/content/article/40/67-color-sun

[ollypenrice]

That's ok. But what excuse do science documentaries with animations that represent The Sun from space have?

I don't know. Proper text books presenting images always indicate the source of the colour seen in the image. This may be 'RGB' (a good approximation of  'natural colour') or it may be a mapping like the Hubble Palette, in which case the assignment of wavelengths to colours will be specified. 

Most amateur solar images are captured either in neutral density or Ha filters, though sometimes the CaK line is captured as well. Since the different wavelengths capture features at different depths into the sun's 'surface' it is important to state the wavelength of the image. I suppose the fact that documentaries don't do this reflects one of the differences between a proper text book and the telly. I know which I prefer...

I think the term 'white light' goes back to Newton and his prism experiments. As others have said, it isn't an accurate term but just a conventional one, meaning 'Sunlight as seen on Earth.'

Olly

[JB80]

One of my favourite little nuggets are that the Sun spots, whilst they appear black are not actually black. It's just the rest of the Sun is so bright they stand out as black. A spot by itself would indeed be quite a bright point of light.

[Knight of Clear Skies]

One of my favourite little nuggets are that the Sun spots, whilst they appear black are not actually black. It's just the rest of the Sun is so bright they stand out as black. A spot by itself would indeed be quite a bright point of light.

Yes, they are cool spots where the Sun's magnetic field inhibits convection, preventing hotter plasma underneath from rising to the surface. Cool being a relative term, you could certainly roast a chicken in one.

[Generalbrick]

"And I don't care what else anyone has ever told you, the Sun is white, not yellow. Human color perception is a complicated business, but if the Sun were yellow, like a yellow lightbulb, then white stuff such as snow would reflect this light and appear yellow—a snow condition confirmed to happen only near fire hydrants." - Neil DeGrasse Tyson

[michael.h.f.wilkinson]

The sun is white, for a given value of "white".

The point is that there is no specific set of stimuli to the red, green, and blue cones in the retina that give us the sensation of "white". Our visual system sets a white point (much like modern DSLRs) depending on the illumination conditions. The "white light" that reaches our eyes when we see a sheet of white paper that is illuminated by direct sunlight (which is almost the same colour as seen from space, unless the sun is very low in the sky), is VERY different from the "white light' reflected of that same sheet of paper when illuminated by an incandescent light bulb. The difference can be appreciated if you look how deep blue an 80a filter is which converts incandescent "white" to sunlight. At night our white point is shifted to the blue even further than in daylight, which is why A stars appear white (Vega), whereas G stars (like Capella) have a yellowish hue. Colour does not really exist out there in the world, it is all in our brain, i.e. a matter of perception.

[RikM]

I don't have a DSLR image to upload but when I have shot colour images through Baader film with a 'daylight' colour balance selected the disc comes out sort of pink. So #FFF5F2 is about right for that sort of image.

I am afraid 'what colour is it?' is very like the question 'what time is it?' There is no single answer. Most documentaries are produced for entertainment reasons, so the sun is presented in a way that seems familiar to the average person. The average person hasn't seen the sun either from space or through a Ha solar scope, so it shown as a bright yellow.

[michael.h.f.wilkinson]

I don't have a DSLR image to upload but when I have shot colour images through Baader film with a 'daylight' colour balance selected the disc comes out sort of pink. So #FFF5F2 is about right for that sort of image.

I am afraid 'what colour is it?' is very like the question 'what time is it?' There is no single answer. Most documentaries are produced for entertainment reasons, so the sun is presented in a way that seems familiar to the average person. The average person hasn't seen the sun either from space or through a Ha solar scope, so it shown as a bright yellow.

Which is a convention perpetuated from kindergarten, where kids take yellow crayon to draw the sun. This is because it is hard to draw a white sun on a white background. They learn that the moon is white and the sun yellow, whereas moonlight is VERY close to sunlight, spectrally.

[acey]

Which is a convention perpetuated from kindergarten, where kids take yellow crayon to draw the sun. This is because it is hard to draw a white sun on a white background. They learn that the moon is white and the sun yellow, whereas moonlight is VERY close to sunlight, spectrally.

Close, but moonlight is redder than sunlight, with a colour temperature of a little over 4000K, whereas sunlight at the Earth's surface is well over 5000K (if the sun is high). Both are still a lot whiter than most artificial lights. In the back-to-front terminology of lighting engineering, sunlight is "cooler" (bluer) than moonlight. We perceive moonlight on the ground as blue, but only because we are relatively unresponsive to red at low light levels.