6 replies to this topic

[foxwoodastronomy]

You folks are going to love this! In 2017, I saw the amazing change to the gray/silvery character of light/color that occurs in the surroundings about 5 minutes before totality. I wanted to study this effect more during the 2019 total solar eclipse, so I did a basic spectral analysis of the Sun by pointing a spectrum data logger at the Sun. At the 2023 annular eclipse, I pointed the spectrum data logger at the observing position, and the data is even more interesting than in 2019. Follow the three images. #1 It is known that the limb of the Sun is a different color than the center of the Sun. With an entire solar disk, the color of the center of the Sun overwhelms the contribution of the limb of the Sun #2 I questioned what happens to the observer's ambient lighting late in the partial phases when the crescent limb of the Sun is illuminating us? It turns out that the wavelengths of light coming to Earth change. I measured it in 2019 and again in 2023 at the annular eclipse. But the annular is fascinating because there is no totality, just a long time being lit by the limb color! #3 The observer is lit by a different percentage of the three wavelengths of light with a shift to the red because most of the Sun's surface, which has a color around 6,300K, is blocked, leaving us to be illuminated by the limb. I don't have an explanation for the two blue spikes that occurred about 15 minutes before C2 and after C3. So, in addition to a decrease in LUX, this wavelength change may contribute to the fact that some observers saw a difference in the character of the lighting during annularity. This wavelength shift is interesting, but at a total solar eclipse, the more powerful effect regarding the ambient lighting color changes is the biochemistry of the Purkinje Effect.

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[timelapser]

Thanks a lot for posting this, Gordon.  I thought about this for the 2023 eclipse but didn't notice any colour shift around annularity.  The colour shift would be gradual during an eclipse, and the eye can quickly adjust to substantial changes in colour balance, as eg when moving from outdoor to artificial indoor illumination, so I'd be surprized if it was noticable at an eclipse.  But the effect will increase the closer to the limb you get, so I'd expect a more noticable effect in the seconds before C2/after C3 at a total eclipse, when just an extremely thin slice near the limb is visible.  I plan to pay attention if I get to see April's eclipse.

 

About your plot #3, I'm puzzled by the perfectly flat curves outside the black vertical lines, and the sudden changes in all three channels near those vertical lines.  This effect should be smoothly increasing as the sun is obscured; it doesn't "turn on" when the sun reaches a certain crescent phase.  Are the black lines when you switched on your spectrum logger?  Also, what exactly are you plotting - the red curve increases towards mid eclipse, so can't be absolute intensity.  What are the curves percentages of, ie they are absolute intensity divided by what?

[Cajundaddy]

Definitely a noticeable shift with the annular eclipse and nearing totality.  My senses tells me that a layer of smoke from forest fires has moved in causing the sky to appear more amber.  Just a color shift as the central area of the sun is obscured. 

Edited by Cajundaddy, 17 November 2023 - 05:00 PM.

[KMH]

Definitely a noticeable shift with the annular eclipse and nearing totality.  My senses tell me that a layer of smoke from forest fires has moved in causing the sky to appear more amber.  Just a color shift as the central area of the sun is obscured. 

Yes, that's a good way to describe what I sensed at and close to annularity.  The feeble light definitely had an orange tint to it.

Thanks for the data, Gordon - very interesting to see quantitative data to confirm this.

 

Kevin

[ch-viladrich]

Nice experiment !

 

What spectrum data logger did you use ?

[foxwoodastronomy]

Nice experiment !

 

What spectrum data logger did you use ?

Sorry for the delay in responding to this.  I used a Pasco Wireless Light Meter Data Logger.

[emh52]

You folks are going to love this! In 2017, I saw the amazing change to the gray/silvery character of light/color that occurs in the surroundings about 5 minutes before totality. I wanted to study this effect more during the 2019 total solar eclipse, so I did a basic spectral analysis of the Sun by pointing a spectrum data logger at the Sun. At the 2023 annular eclipse, I pointed the spectrum data logger at the observing position, and the data is even more interesting than in 2019. Follow the three images. #1 It is known that the limb of the Sun is a different color than the center of the Sun. With an entire solar disk, the color of the center of the Sun overwhelms the contribution of the limb of the Sun #2 I questioned what happens to the observer's ambient lighting late in the partial phases when the crescent limb of the Sun is illuminating us? It turns out that the wavelengths of light coming to Earth change. I measured it in 2019 and again in 2023 at the annular eclipse. But the annular is fascinating because there is no totality, just a long time being lit by the limb color! #3 The observer is lit by a different percentage of the three wavelengths of light with a shift to the red because most of the Sun's surface, which has a color around 6,300K, is blocked, leaving us to be illuminated by the limb. I don't have an explanation for the two blue spikes that occurred about 15 minutes before C2 and after C3. So, in addition to a decrease in LUX, this wavelength change may contribute to the fact that some observers saw a difference in the character of the lighting during annularity. This wavelength shift is interesting, but at a total solar eclipse, the more powerful effect regarding the ambient lighting color changes is the biochemistry of the Purkinje Effect.

Really interesting, so imagine that the shift would be more dramatic if the eclipse was low in the sky compared to the about 60 degrees of the past annular ? And this would then account for the enhanced visual effects seen in TSE ore ASE near the horizon ?