Sun is shown 'too yellow' in media

[skysurfer]

In books, websites and planetarium software, the sun is shown in yellow which is not the reality. If it is yellow (or even reddish) then it is the scattering of blue light from the Earth's atmosphere.
High in the sky it is white.
A light bulb is actually yellowish, but that is 'only' 2700 K, but the sun is 5700 K.

Even F stars (7000-8000K) are shown as 'yellowish' but in the real world they are white with even a bluish tinge. This can easily be seen in bright F stars (Canopus, Procyon), particularly by observing with a telescope. Even bright G stars (Alpha Centauri, Capella) 'lose' there 'yellow' tinge when viewed with a telescope.
Strange enough that Capella in *daylight* does have its yellowish tinge but that is probably contrast to the blue sky.
A light bulb (or CFL energy saving lamp) from 1km away looks like a red M star, but when you view for example Betelgeuse with a 10cm or larger telescope it looks more yellowish. So the brightness has also an influence.

What are your ideas on this?

[naskies (Dave)]

I think it's probably because the only time that most people are able to see the solar disc is usually during a sunset. I personally like seeing a golden or red colour in the images posted on here.

[Astroman (Andrew Wall)]

I also think the colour yellow or orange adds warmth to the Sun. We have all grown up seeing those books etc... with the sun pictured in colour, I think it continues on through life. If we show a white sun, it wouldn't be as eye catching... I must admit, I have coloured my pictures of the sun to reflect the typical look what we see in books etc.... No harm in it.

[Nico13 (Ken)]

I had added some colour to my images not only because I liked the look of it but it helps in image sharpness and overall contrast that allows better granulation to show in the image as I only have Baader film filters.

[Zhou (Mick)]

True the Sun is white but yellow is the colour we generally percieve it to be. To be honest I prefer diagrams, images and representations of the Sun to be in yellow even though it is not exactly scientifically correct.

[sheeny (Al)]

Do you ever wonder why there are no green stars?

The colour of a star is determined by the peak in the continuum of the star's spectrum according to Wien's Law.

For our sun, the peak is in the green part of the spectrum. We have however evolved to perceive the particular blend of frequencies our sun puts out as white. So we perceive all stars with similar spectra as white, and we do not recognise green stars.

Therefore the correct colour of the sun is green, based on Wien's Law, however, stars of this temperature have historically been called yellow.

Al.

[Poita (Peter)]

So if I took a picture through solar film with a colour camera, and checked the RGB values, then the image would lean towards the green?
I like the description on this site, especially how Japanese children will often colour the sun red when drawing it...
http://solar-center.stanford.edu/SID.../GreenSun.html

As for colouring of images, I love the golden looking ones for a couple of reasons.

1) With the colour added, I find it easier to see the details than with a monochrome image.

2) It feels pleasing, creating the sort of emotional feeling I get when viewing a sunrise or sunset.

So I am okay with the false colour images generally.

[erick (Eric)]

Everyone expects to see a yellow Sun, based on childhood drawings, so I regularly put a yellow filter on the eyepiece for public viewings of the sun.

[brian nordstrom (As avatar)]

True , but Antares small companion looks very green to me every time I've managed to spot it , a contrast effect ?
Brian.

Originally Posted by sheeny

Do you ever wonder why there are no green stars?

The colour of a star is determined by the peak in the continuum of the star's spectrum according to Wien's Law.

For our sun, the peak is in the green part of the spectrum. We have however evolved to perceive the particular blend of frequencies our sun puts out as white. So we perceive all stars with similar spectra as white, and we do not recognise green stars.

Therefore the correct colour of the sun is green, based on Wien's Law, however, stars of this temperature have historically been called yellow.

Al.

[sheeny (Al)]

Originally Posted by Poita

So if I took a picture through solar film with a colour camera, and checked the RGB values, then the image would lean towards the green?

No.

White light from the sun, has a certain shape across the spectrum. It is not a flat line across all the frequencies. The peak intensity of white light is in the green part of the spectrum. For red stars, the peak intensity is near the red end, for blue it is near the blue end. So, following Wien's Law, as I say, all white stars, have their peak intensity in the green part of the spectrum and are therefore technically green.

Some "white light" solar filters have a colour cast about them. That is, they don't block the same proportion of photons at all frequencies across the spectrum, the closer they are to flat linear (same proportion of photons blocked at all frequencies) the closer the image of the sun will appear to white.

Cameras, you must keep in mind, are manufactured to replicate what we see. So a colour photo through the white light solar filter, shouldn't look any different to what you would see, but often of course it does to varying extents depending on how well the manufacturer has built the camera to replicate what you would expect to see, and how you have various settings, such as colour/white balance, set, etc.

Am I explaining myself any better?

So a peak intensity at green does not mean we see green. If the shape of the spectrum matches the sun, it will appear white. If the peak is steeper than the sun it will appear green. If the peak is flatter than the sun's spectrum, it will appear pink (Pink = white - green).

Even mono cameras often have peak sensitivity around the green part of the spectrum. This provides a mono image which is appealing to the eye, and this means we have to correct for the "instrument response" to do valid scientific measurements in spectroscopy.

Clear as mud?

Al.

[sheeny (Al)]

Whoops!!!!



My apologies Brian!

I've just read you post again and for the first time read "Antares small companion" not "Antares".

Who is it that needs to get their eyes checked???

Sorry mate!



I can't say I've noticed the colour of Antares small companion, but if its the same temperature as the sun, it will appear white. Not sure what effect being a little bit hotter (probably) or cooler than the sun would have, but you generally don't here about green stars (because they are white).

I think you might be right about the contrast effect, though. If so, you could test the hypothesis by moving Antares just out of the FOV (or occluding it - maybe not so easy to do?). Once Antares is out of view, it should look white.

Al.

Originally Posted by sheeny

It looks really red/orange to me. I can't say I've heard of it being seen as green. I don't want to sound like I'm have a go at you, cause I'm not, but have you been tested for red green colour blindness?

I could understand an occasional green flash when its low in the sky or during bad seeing...

As an afterthought, I would suggest that the reason sun is historically portayed as yellow probably has to do with seeing it late in the arvo and early in the morning, through more atmosphere which scatters away the blue light. Purely a speculative, guess on my part.

Al.

[Zhou (Mick)]

The companion to Antares has always looked white to me. The perception of colour is such a subjective thing.

[brian nordstrom (As avatar)]

No worries Al , we all have our dyslexisc moments , me ,well ? all the time ....
And Zhou , you are right there , but how do you se the colours in the traffic lights in the middle of the jewl box ?
I see red , orange and green very clearly in my 127mm apo , its a great effect . .
Brian.

[Poita (Peter)]

Originally Posted by erick

Everyone expects to see a yellow Sun, based on childhood drawings, so I regularly put a yellow filter on the eyepiece for public viewings of the sun.

Unless they are Japanese, in which case they expect to see red from childhood drawings. Culture also plays a part in perception.

[Zhou (Mick)]

Originally Posted by brian nordstrom

Zhou , you are right there , but how do you se the colours in the traffic lights in the middle of the jewl box ?
I see red , orange and green very clearly in my 127mm apo , its a great effect . .
Brian.

I can't say I have noticed the traffic light effect in the Jewel Box, the "green" star has always appeared white to me and I have viewed the cluster through many types of telescope.

It is said that some people percieve the star Beta Librae (Zubeneschamali) as green. Again to me it looks white.

Sadly it looks like I may never see any green stars

[sheeny (Al)]

Originally Posted by brian nordstrom

No worries Al , we all have our dyslexisc moments , me ,well ? all the time ....
And Zhou , you are right there , but how do you se the colours in the traffic lights in the middle of the jewl box ?
I see red , orange and green very clearly in my 127mm apo , its a great effect . .
Brian.

I can't say that I've ever seen or heard of the traffic lights in the jewel box. The ruby stands out...

If I ever get clear skies again I'll have to have a look for it!

Al.

[brian nordstrom (As avatar)]

yep Zhou , Zub ..... in libra , I have looked at all the stars in Libra , me being a Librean , and have seen it as orange , nice double that one .
I supose , as Kermit sang , " Its not easy being green " ? .
My refractors show green stars sometimes under good seeing , aye ? Al .
Very subjective , but nice at the eyepiece ..
Brian.

Originally Posted by Zhou

I can't say I have noticed the traffic light effect in the Jewel Box, the "green" star has always appeared white to me and I have viewed the cluster through many types of telescope.

It is said that some people percieve the star Beta Librae (Zubeneschamali) as green. Again to me it looks white.

Sadly it looks like I may never see any green stars

[sheeny (Al)]

Originally Posted by brian nordstrom

My refractors show green stars sometimes under good seeing , aye ? Al .

I have a set of binoculars like that... but, ssshhhh... say no more, or everyone will want one.

Al.

[Zhou (Mick)]

I definately cannot see any green stars (DSO's are a different kettle of fish). However, I have no problem seeing red. I saw some red shadings in M42 many years ago when I was using my 350mm dob near Oberon. I also suspect I may have seen a red hue in Proxima Centauri despite its faintness.

http://www.iceinspace.com.au/forum/s...ad.php?t=93988

[Paul Haese]

At the risk of starting something here I respectfully disagree regarding how us solar imagers portray the colour of Sol. It is a yellow star. Click here for NASA page.

If Sol is supposed to be very similar to Rigel Kentaurus and its smaller twin then when I view that star through a telescope it appears as an orangey yellow colour. I have heard many people say it appears as this colour. While the colour of Antares is slightly more red and more orange. Antares's twin appears green to me, but most likely this is due to the orange fresnel rings mixing with the white light of the pup.

Anyway feel free to respond.