The following is the latest in the Quest for the Color of the Sun.

Since this heliochromological quest will probably be a BAUT exclusive, it is probably wise to articulate its latest developments in anticipation of the fateful day, hopefully, in the not too distant future.

Of course, there are numerous other threads regarding the sun's possible color, but as we approach the day of colorful fruition, perhaps a more concise thread would be appropriate (i.e. this one ). We should appear more polished when the masses flock here once they learn there is a definitive answer to this polemic issue which may have first started with the ancient discovery of our luminous orb.

First, allow me to explain how an irrefutable claim of the sun's color will be justified. An instrument, colorimeter, will reconstruct the solar spectrum to match the sun's spectrum as observed from space. In other words, every separate spectrum color - violet, blue, green, yellow, orange, and red - will end up having the same intensity level relative to each other color as the intensity level of sunlight as observed from space. Since our atmosphere absorbs and scatters colors unevenly, these color levels must be restored to the level they were before sunlight entered our atmosphere. Some colors scatter more than others; which is why the sky is blue.

Thanks to solar telescopes in space, much is known regarding the intensity of sunlight for each wavelength. A final color spot will be generated and it will have the same intensity for each wavelength as sunlight observed from space. [The intensity level for each wavelength is known as spectral irradiance.]

Fortunately, this reconstruction of sunlight received can be tested for accuracy. The following illustrates the principle that will be used to accomplish the task of producing a near perfect color spot equivalent to the sun's true color. The unique instrument that will perform this task is now called a colorimeter. [Name given by Dan Bruton of SFASU.]



Explanation:

A ~ Sunlight entering the tube, B, is comprised of all the colors of the spectrum. It is important to know the intensity level of each wavelength of this entering sunlight. This has been established and is found as spectral data of the sun taken when the sun is at different altitudes.

B ~ Two slits cause a narrow, rectangular beam, C, to enter the subsequent prism, D.

C ~ Using a narrow beam is important to minimize the smearing of colors after they become dispersed from the prism. Too broad a beam will cause bleeding of colors onto other colors.

D ~ An F2 prism with known indexes of refraction, to five decimal places, for many wavelengths is used. Interpolations are done to establish the exit angle from the prism of each wavelength.

E ~ These are the colors of the sunlight but, recall, their intensity levels have been reduced unevenly due to our atmosphere.

F ~ Since we know the level of reduced intensity of the sunlight for each wavelength that enters and exits the prism, and we know the intensity of each wavelength they must reach in order to be at a level they were before entering our atmosphere, we can construct a mask which restricts the amount of each color as necessary to produce the original intensities as seen from space. For example, if more blue is needed relative to red, we will restrict the amount of red light passing through the mask. In effect, this alters the intensity level of each color relative to all the others. Fortunately, this can be done for all wavelengths relative to each other.

G ~ The colors passing through the mask will have the same relative intensities as the colors produced by the sun.

H ~ In the past, recombining this spectrum has not be accomplished well enough to produce a definitive result. An array of thousands of 0.25mm fiber optic strands will receive the adjusted color levels and scramble them around to help homogenize the final color. This will be the newest addition to the colorimeter.

I ~ It is hoped the output from the fiber will appear homogenized as it enters a lens.

J ~ A double convex lens will reduce the light beam into a small spot to minimize our ability to distinguish separate colors.

K ~ A white spot located on a black plate will reflect the final color spot. This allows us to see the result. Our eye and brain will do the rest, just as it normally does. This eliminates the need for computer modeling of colors. It might help calibrate existing models, however.

X ~ of course, it's the spot.

S ~ A calibrated spectrometer will verify that the spectral irradiance of our spot will properly match the spectral irradiance of the sun as seen in space. If it does not, we will know what wavelengths need correcting and the mask will be easily altered accordingly. [Advice on how to borrow, rent, or own a spectrometer will be appreciated. I found one with accessories for $2k, but I hope not to have to spend so much.]

Once there is a match, the spot we see will represent the color of the sun!

This will not end heliochromology, however. Ths sun has a temperature difference from center to limb of about 1,390K. Thus, the solar disk may not be as uniform in color as we might expect. The central region may have a slightly different color than the outer regions. I have hope people I've contacted will help find the spectral irradiance data needed for rendering color for these solar regions.

I will try and get a picture of the colorimeter mounted on an 8 inch SCT soon. It is crude and for a reason. NASA could simply take up a strobe, or other attenuation device, and eliminate all this effort; so it lacks some appeal. Of course, it is just a prototype.

Well, that is the latest. Is the explanation understandable?

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.