How to Observe - Light

Image from the website SunCalc.net A really neat resource to see the sun movement and sunlight phases during a specified day at specified location.

Observing Light Patterns

Sunlight is the most important factor to our existence, without the sun we could never be. It is just the right temperature for creatures like us, it nourishes plants - as well as us (vitamin D), it evaporates water from our oceans allowing rain and snow to shower down, without it our planet would be a lifeless ball of ice-coated rock.
This past year, with the eclipse crossing the US many people took the time to observe the sun and the interesting patterns it cast on the ground during the eclipse, and it was awesome, but what about the other times of the year? We assume the sun doesn’t change too much, its timing may differ but it rises every morning, sets every night, life goes on and you don’t need to be too concerned about the sun. That being said, it is interesting to observe, and there is a lot more to observe than you may think…

• Light Patterns - Consider how you see the light throughout the day, when do you notice it most? What about it makes you aware of it?
  • Times of Day - there are 4 main easily definable times of day that we’re all familiar with, but did you know there are 3 others that play an important role too!
    • Sunrise - Easily one of the most beautiful times of the day. It takes the sun approximately 3 minutes to rise. 
      • Notice the color of the light, are there any clouds that are reflecting the color of the light? Is the sunrise bright and colorful or is it pretty mild? As the sun gets higher and the air gets warmer you’ll find that the wind has a tendency to pick up - this is why you’ll find many photographers prefer to take sunrise photos over sunset photos, especially when attempting to shoot still bodies of water.
    • Daylight - Daylight is so often taken for granted, even when obscured by clouds it diligently illuminates our world. Take a day and look at where the light casts shadows at different times, you’ll notice just how fast the light can change - anyone who has attempted to sunbathe near trees can tell you this! 
    • Sunset - As with sunrise, a truly beautiful 3 minutes of every day. Most of the qualities of sunrise are the same as sunset, however, after a day of a stirred up atmosphere, dust, and pollutants, sunsets can show a larger area of colors. “At dawn, clearer skies enable more brilliant reds and oranges to make their way through the atmosphere to your eyes, whereas thicker atmospheres at dusk tend to dull these colors, leading to more washed-out sunsets. On the other hand, more dust and smog (at sunset) can have the effect of scattering light across a greater region of the sky, creating a larger drape of colors, whereas sunrise colors tend to be more focused around the sun. Whichever you prefer, you can frequently tell a sunrise from a sunset by the fact that the latter appears more chaotic, and the former, tidier.” https://www.livescience.com/34065-sunrise-sunset.html
    • Night - Obviously the light is very different at night, it is a time for sleep for some and a time for awakening of our nocturnal friends. 
    • Other interesting times of day that you may not be aware of.
      • Astronomical Twilight - the first stage moving from night to sunrise (or the last stage from sunset to night) “…occurs when the Sun is between 12 degrees and 18 degrees below the horizon.”
      • Nautical Twilight - “occurs when the geometrical center of the Sun is between 6 degrees and 12 degrees below the horizon. This twilight period is less bright than civil twilight and artificial light is generally required for outdoor activities.”
      • Civil Twilight - the last stage from night to sunrise (or the first stage from sunset to night). “…occurs when the Sun is less than 6 degrees below the horizon. In the morning, civil twilight begins when the Sun is 6 degrees below the horizon and ends at sunrise. In the evening, it begins at sunset and ends when the Sun reaches 6 degrees below the horizon.””Civil twilight is the brightest form of twilight. There is enough natural sunlight during this period that artificial light may not be required to carry out outdoor activities. Only the brightest celestial objects can be observed by the naked eye during this time.”

 

• Times of Year - As the earth tilts on its axis, we get longer days in the summer and shorter days in the winter, the pinnacle of these times are the solstices. At the time of writing this it’s late December, notice how even at noon the sun sits low in the south casting long shadows, revisit this observation in the summer and you’ll find very little shadow at noontime.
  • Summer Solstice - The time when the sun reaches its highest altitude of the year, the “longest day of the year” meaning most daylight (still 24hrs in a day). 
  • Winter Solstice - Just happened less than a week ago on Dec 21st, when the sun’s maximum elevation in the sky is at its lowest causing the “shortest day of the year” - least amount of sunlight in a day. This time of year you’ll be able to notice how trees seem to always be casting long shadows.
    
    
• Weather - Even when the weather changes, you can always tell daylight from night (okay, except in very extreme cases). Rainy, snowy, and overcast days provide an interesting chance to observe how clouds diffuse the light, notice how soft shadows become in comparison to how sharp they appear in direct sunlight, does the light differ between snowfall and rain?
  
  
• Light Color - Simplified, there are “cool colors” (colors that appear blueish white), there are "warm colors” (colors that appear yellow or orange), and all the colors in-between. The sun is generally between 5000K (“warmer” (yellower) horizon daylight) and 15000K (“cooler” clear bright blue poleward sky).
  An easy way to observe light color is to look out at the snow. Notice where the sunlight shines directly on the snow, then look to where the snow is in a shadow, you’ll see how the snow in the sun is a whiter color where as the snow in the shadow, by comparison is bluer! The color differences can be very apparent when fluorescent or incandescent or even candle lights are mixed or mixed with daylight - consider the warm glow of candle light even when house lamps are on.
  • Kelvin scale is the method in which light color (light temperature) is measured - 1700k = match flame is a very warm color, 27000k = clear blue sky is a very cool color. This is important to know for many reasons - in photography, to assure accuracy of an image you need to match the Kelvin color in camera (white balance) to the color of the scene - in raising fish or plants without natural light they need a very specific k-color to imitate natural light to grow.

 

• Health - You can even observe how sunlight affects your health.
  • Daylight exposure is vital to maintaining a regular circadian rhythm which works with your body’s chemistry to provide you a better night’s sleep!
  • It can also increases the serotonin levels in your body making you more active and alert.
  • Studies have shown that exposure to UV rays releases nitric oxide that lowers blood pressure. 
  • The most notable benefit is sunlight’s ability to boost your body’s vitamin D supply. A healthy supply of vitamin D promotes bone growth and prevents illnesses such as breast and colon cancer, inflammation, MS, seasonal disorders, and depression!

Yes, the sun does more than create beautiful light and shadow patterns, today go out with a renewed sense of all the factors that play into our existence thanks to that bright star in the sky!


References/links for more info:
Different types of twilight -
     https://www.timeanddate.com/astronomy/different-types-twilight.html
Differences of Sunrise and Sunset - 
    https://www.livescience.com/34065-sunrise-sunset.html
Atmospheric Optics - 
    https://en.wikipedia.org/wiki/Atmospheric_optics
The Sun and Us - 
    https://history.nasa.gov/EP-177/ch3-1.html
Health benefits of sun exposure - 
    http://www.medicaldaily.com/sun-exposure-vitamin-d-and-other-health-benefits-sunlight-246487
Color Temperature - 
    https://en.wikipedia.org/wiki/Color_temperature
Sun Calculator  - 
    http://suncalc.net/