Wonders Of The Sky

"Sometimes gentle, sometimes capricious, sometimes awful, never the same for two moments together; almost human in its passions, almost spiritual in its tenderness, almost Divine in its infinity." -John Ruskin, The True and Beautiful, The Sky

Our sky is full of wonders. Ever changing, unpredictable display of nature’s art. But we often don't pay too much attention to the sky above our heads nor usually have that much knowledge about the basic physics behind even some of the most common phenomena out there.

Just alone the constantly reforming clouds can be a joy and an endless inspiration for painting and photographing, not to mention the sunrises and sunsets and their colors, or the stars and Auroras in the night sky.

Nowadays though, the night sky is largely light polluted and really dark starry skies with shining milky way, the kind our ancestors were admiring, are hard to find nowadays. But there are also plenty of mesmerizing daytime phenomena to be seen on our skies that are worth capturing or at least worth seeing and experiencing.

My fascination for the sky grew a lot after discovering photographing at the age of 20. By that time, I also discovered websites like spaceweather.com and atoptics.co.uk, which have been a source of information and inspiration for observing and photographing the sky. Ever since, I've been chasing and capturing all kinds of beautiful phenomena. Most of the time I really have to hunt for some phenomena, but sometimes I just end up having a camera with me and some good old luck. It's also really useful, sometimes even necessary, to have some background knowledge about the phenomena, to know for example where and when to look for a certain one. And to me it’s just so much more fascinating to understand the science behind of it all.

Here's some of my shots of our fascinating sky with some background information and simple explanations about the phenomenon in them.

Like Charlie Chaplin sang in his own song in the opening of the re-release of his movie The Circus:

"Look up to the sky, You'll never find rainbows, If you're looking down."

(For this article I've used sources like Wikipedia, NASA, spaceweather.com, atoptics.co.uk)

Auroras must be the most spectacular phenomenon of them all. A proper geomagnetic storm will surely take your breath away.
The one in the photo, witnessed in Signaldalen, N-Norway, surely did that to me! It's taken during a moderate G2-class Geomagnetic Storm that lasted from dawn till dusk.

Auroras occur in two ovals encircling the magnetic poles, and the source for them is the Solar Wind, high energy plasma that's constantly escaping the Sun's gravity with speeds ranging from 200km/s up to more than 1000km/s.
To produce vivid Auroras, the Solar Wind often needs a boost, either via Coronal Mass Ejection or from a Coronal Hole.
When this boosted Solar Wind, that is dragging the Sun's magnetic field with it, hits the Earth’s magnetic field, the fields partially connect, and the particles get accelerated towards our atmosphere, spiraling down along the magnetic field lines that come in and out around the poles. Then the highly energized particles collide with the upper atmosphere’s atoms and molecules (mostly oxygen and nitrogen) producing ionisation, dissociation and excitation. The clouds of excited atoms and molecules radiate their excess energy as photons, producing the glowing and shifting Auroras.
Most of the light comes from electronically excited oxygen atoms. Yellowish green (557,7nm) radiation prevails at around 120-180km high and above that the less excited O-atoms radiate red(630nm)light. Excited nitrogen molecules and nitrogen molecular ions produce pink and red at low altitudes. Most excitation is by collisions with electrons.

When photographing the Auroras, the exposure times and settings vary greatly due to the different intensities in the displays. Sometimes when you can barely see a colorless haze on the horizon, you can easily see the color with a proper exposure. But sometimes when the display is really intense, the movement can be so fast that it’s impossible to freeze it, even with just few second exposures. Those are the truly mind blowing times when it’s best to just admire it with your naked eyes.

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Location: Signaldalen, Storfjord, Troms, Norway
Date&Time: 1st of Mar 2017 23:31(local time UTC+1)
Gear: Nikon D600 & Samyang 14mm f/2,8
Benro A2980T-tripod & B1-Ballhead
Settings: | 14mm | f/3,2 | 5s | ISO 3200 |
Daylight-white balance for natural colors
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Dark star filled night skies are definitely one of the most mesmerizing sights to behold. Even more so because sadly now days the light pollution from our artificial lights ruin the night skies over populated areas.

The accumulated starlight from the direction of the center of the Milky Way shines bright in this photo taken in Flores, Azores, under almost light pollution free skies. The dark regions are caused by interstellar dust blocking the incoming light.

The green and red haze above the horizon is Airglow.
Airglow, like Auroras, is mostly produced by excited gas atoms and molecules in the upper atmosphere. But unlike auroras, which are caused by collisions with energetic charged particles guided and accelerated by the Earths magnetic field, Airglow is produced by daytime short wavelength solar radiation via chemical excitation in which electronically excited oxygen atoms are the main component. So Airglow can be seen anywhere when the conditions are right and the sky is dark enough/free of light pollution. Although the light is never strong enough to active human color vision, and is very difficult to see with unaided eye. So that's again something that camera can show that the eye can't.
The sources for the specific wavelengths are pretty much the same as in Auroras (mentioned earlier).

There's also a meteor aka shooting star captured in the photo. It's most likely a member of the annual Perseid Meteor Shower. Meteors are caused by tiny cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds. The drag of the air on the rock makes it extremely hot, and the bright streak is actually the glowing hot air as the burning rock zips through the atmosphere.

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Location: Flores, Azores, Portugal
Date&Time: 18th of Aug 2017 01:30(local time UTC+0)
Gear: Nikon D750 & Sigma 35mm f/1,4
Benro A2980T-tripod & B1-Ballhead
Settings:
Sky made of 3 horizontal frames with:
| 35mm | f/2 | 10s | ISO 3200 |
Landscape: | 35mm | f/2,8 | 119s | ISO 3200 |
Daylight-white balance for natural colors
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Proper thunder strom is always something awe-inspiring.

Lightning is an electrical discharge caused by imbalances between storm clouds and the ground, or within the clouds themselves. Nature seeks to balance the imbalance by passing current between the differently charged areas.
Lightning is extremely hot - a flash can heat the air around it to temperatures five times hotter than the sun’s surface. This heat causes surrounding air to rapidly expand and vibrate, which creates the pealing thunder we hear a short time after seeing a lightning flash.

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Location: Varkaus, Finland
Date&Time: 14th of Jun 2009 00:37(local time UTC+3)
Gear: Nikon D80 & Nikkor 18-70mm f/3.5-4.5
Benro A2980T-tripod & B1-Ballhead
Settings: | 18mm | f/3,2 | 5s | ISO 3200 |
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The colorful Rainbows have always captivated and mesmerized humans for a good reason.

While being a fairly common phenomenon, there's also something not so common about this one.
Below the primary bow there's clearly visible the so called Supernumerary Rainbows (the thinner stripes).
Unlike the actual rainbow which is caused by refraction and reflection of light in water droplets, supernumerary rainbows can’t be explained by geometric optics.
They are caused by the wave-nature of light - interference between different wavelengths of light following slightly different paths with slightly varying lengths within tiny same-sized raindrops.

In this picture you can also see the phenomenon called Alexander’s dark band. It's an optical phenomenon associated with rainbows where the sky between the primary and secondary bows is darker than elsewhere. It occurs due to the deviation angles of the primary and secondary rainbows. Raindrops along lines of sight between the two bows cannot send light to your eye and so the sky is darker there.

The light reflecting from the Moon can also produce rainbows (Moonbows), but of course not with such intense colors.

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Location: Kuusamo, Finland
Date&Time: 23rd of May 2010 21:12(local time UTC+3)
Gear: Nikon D80 & Nikkor 18-70mm f/3.5-4.5
Settings: | 70mm | f/5 | 1/100s | ISO 100 |
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When thin clouds roll in front of the Sun or the Moon, it's good to check the sky for a phenomenon called, the Corona.
It's a lot less known phenomenon than the colorful Rainbow for example, but can be equally striking and beautiful.

Coronae are rainbow-colored rings around the source of light. Tiny water droplets or ice crystals diffract the incoming light.
This particular Corona was exceptionally distinct, and numerous diffraction rings can be seen because the cloud was newly formed and so (in this wintery case) the ice crystals were all quite uniform.
The rings in this corona are slightly off center because of a gradation in the crystal sizes in the cloud.

The Moon is especially good for this phenomenon, since it's much easier and a lot safer to be looking straight at the Moon rather than the Sun. When the circumstances are exceptionally good, usually newly formed cloud with almost exactly the same sized small droplets, you can see numerous repeating layers of rings, like the ones in this photo taken in N-Finland.

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Location: Kuusamo, Finland
Date&Time: 30th of Oct 2009 20:31(local time UTC+2)
Gear: Nikon D80 & Nikkor 18-70mm f/3.5-4.5
Benro A2980T-tripod & B1-Ballhead
Settings: | 31mm | f/4,5 | 8s | ISO 200 |
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Pollen can form an optical phenomenon called Corona just as well as water droplets or ice crystals. They just need to be tiny enough to diffract light. And because they are copies of each other, when there's plenty of it in the air to assemble and arrange in a way that most of them are facing the same direction, they indeed can produce corona-effect.

Because pollen grains are non-spherical and comparatively large, they produce elongated and small coronae, sometimes with bright patches on their rings.

Coronae from Pine pollen are the most famous, probably because Pines release their pollen in huge quantities and the pollen size and shape is good for producing vivid coronae, like this one photographed in N-Finland in May.
You can also see some iridescence in the clouds around the Sun (which is actually pieces of full corona produced by the water/ice in the clouds).

Different pollen produce slightly different kinds of coronae.
For spotting one it's good to have sunglasses and to block the Sun with something, for example your stretched arm or a building and look just next to the Sun. It's also always good to check and take advantage of reflections, on water for example.

It's necessary to be cautious with any coronae around the Sun as everyone knows it's not recommended to look at it with the naked eyes, neither through a camera viewfinder.
Naturally with Moon the case is different.

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Location: Kuusamo, Finland
Date&Time: 11th of Jun 2010 20:31(local time UTC+3)
Gear: Nikon D80 & Nikkor 18-70mm f/3.5-4.5
Settings: | 70mm | f/4,5 | 1/2000s | ISO 100 |
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Colors in the sky, more accurately on the clouds.
In fact Cloud Iridescent or Iridescent Clouds are fragments of the Corona phenomenon. They are a fairly common, though it seems many are unaware of them. Probably because they often occur fairly close to the Sun, which adds a risk in observing the phenomenon.

You can use your straightened arm, for example, to block the Sun. Sometimes you might also see a lonely colorful cloud further away from the Sun. Also reflections reveal the colors that are otherwise nearly impossible to see because of the brightness of the nearby Sun. Sunglasses also help in seeing the bright colors. It also makes observing a lot easier, if the Sun is behind a house or mountain for example, as in the case of this photo taken in the Swiss Alps.

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Location: Lauterbrunnen, Switzerland
Date&Time: 13th of Oct 2013 16:06(local time UTC+2)
Gear: Nikon D600 & Nikkor 24-120mm f/4
Settings: | 120mm | f/8 | 1/2500s | ISO 200 |
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Whenever the sky is hazed with thin high cirrus clouds it's possible to spot some sort of a Halo. The brighter and more vivid Halo displays can truly be magical sights, as was this beautifully perfect 22° Halo photographed in May in Finland.

The 22° radius circular Halo and Sundogs (Parhelia) are the most frequent Halos. They forms as sunlight is refracted and reflected by in tiny ice crystals suspended in the atmosphere.
The slightly colored thin ring of the 22° Halo around the Sun or the Moon appears more often than Rainbows.

In folklore, Halos are said to have been a warning of approaching rains. It has some truth to it, as cirrus clouds are often pushed on the advancing edge of a warm front with its associated heavy rain, but a Halo is not at all a reliable sign of bad weather coming the observer's way.

If there's nothing to hide the Sun behind, you can block the Sun with an extended arm. Sunglasses also makes spotting easier and more pleasant, and reflections are always safe.

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Location: Vantaa, Finland
Date&Time: 2nd of Jun 2009 12:34(local time UTC+3)
Gear: Nikon D80 & Nikkor 18-70mm f/3.5-4.5
Settings: | 18mm | f/9 | 1/1600s | ISO 100 |
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..is an optical phenomenon where colored rings appear around a shadow of the observer in cloud or fog. The science behind is complicated and still not fully solved, but simply put, the light is scattered backwards by tiny water droplets, and it involves reflection, refraction and diffraction of the light.

Glories always appear in the antisolar point, so each observer has their own, and that's why they're also seen most often when you have a view downwards, e.g. from a mountain or from an airplane.
Glories in the clouds around the shadow of an airplane are probably the most common ones. So, next time take a seat opposite to the Sun and watch them ring the plane's shadow - or more accurately, where your own shadow would be.

This Glory was photographed from the Highlands of Flores in Azores as the Sun was just setting behind the ridge I was on.

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Location: Flores, Azores, Portugal
Date&Time: 17th of Aug 2017 19:58(local time UTC+0)
Gear: Nikon D600 & Nikkor 24-120mm f/4
Settings: | 24mm | f/8 | 1/320s | ISO 200 |
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Quite rarely, just before going below the horizon, the top part of the Sun can suddenly show a green, and very rarely even blue flash on its top. It normally lasts only a second or so and requires special atmospheric conditions.
The Green Flash is caused by the same atmospheric refraction and scattering effects which produce the red sunset. Green light is refracted more strongly than red and so different colored images of the sun become very slightly vertically separated. As the sun sinks it develops a green (blue light usually gets scattered away from the rays) upper edge and a red lower one, but the
effect is small and cannot be seen with the unaided eye. To make a Green Flash visible, these tiny refraction effects need to be considerably magnified by a Mirage. For a mirage to be seen, there needs to be the right temperature differences in the air layers, and a right viewing angle, usually a low horizon-view.
Most often Green Flashes are seen over open ocean, but rarely as in these photos taken in wintery Finnish Lapland, they can be seen over land as well when the conditions are right.

Once again eye protection is important!

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Location: Kuusamo, Finland
Date&Time: 19th of Feb 2010 16:54(local time UTC+2)
Gear: Nikon D80 & Nikkor 300mm f/4
Settings: | 300mm | f/8 | 1/640s | ISO 100 |
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On latitudes between 50-70° on a summer night it's possible to witness electric-blue wavy clouds. These elusive night shining clouds, that are not that well understood even by the scientist, might often go unnoticed. Sometimes when the display is really strong though, it's hard to miss and not to wonder them, for they don't look like ordinary clouds. And they aren't like any ordinary clouds..

These mysterious clouds are formed by tiny ice crystals in altitudes around 76 to 85 kilometers, in the atmospheres
least studied part called the Mesosphere. Mesosphere is also the driest and coldest part of our Atmosphere. It’s hundred million times drier than the air of Sahara!
The sources of the water the nuclei, around which the ice has to form, are not known with certainty. Meteoric, volcanic and tropospheric dust are the likely candidates. Clouds might even be able to form directly from water vapor in the mesosphere.
In the extremely dry mesosphere temperatures below −123 °C are needed to form ice crystals. And summer is the time when, counter-intuitively, the mesosphere gets coldest (enough around the polar regions to form ice). Inside the polar circle though it's too bright to view them in the summer because the Sun is never low enough under the horizon at this season. But bit more south where the Sun dips lower but not too low, it's possible to view them all night.

To me the most curious thing about these electric blueish wave-like clouds is that the first recorded sightings of them were made in 1885. That's two years after the eruption of Krakatoa volcano and also around the time when the Industrial Revolution was kicking
in. Ever since they have remained and become more frequent, brighter and visible at lower latitudes.
Greenhouse gases are predicted to cool the upper atmosphere, and methane emissions produce more water vapor in the upper atmosphere..just what you
need for more Noctilucent Clouds (plus maybe some space dust).
Perhaps noctilucent clouds are kind of Miner's Canary for climate change.

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Location: Archipelago NP, Finland
Date&Time: 2nd of Jun 2015 01:24(local time UTC+3)
Gear: Nikon D600 & Nikkor 24-120mm f/4
Settings: | 24mm | f/4 | 1/6s | ISO 400 |
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Sirius is the brightest star on our night sky. In Ancient Greek "Seirios" meant "glowing" or "scorcher".
As a white dwarf star it shines white light (all the colors of the visible spectrum) and when low on the horizon, disturbance in the atmosphere separates the different wavelengths making it twinkle in all the colors of the rainbow.
With a long exposure and a little movement of the camera it's easy to see the effect.
Many other stars make the same effect, but since Sirius is the brightest one and
it's always low on the horizon here in the north, the effect is the most obvious.
This effect is really easy to catch with almost any camera and you can even do it hand held (since the point is to move the camera in order to get the "line of colors").

Sirius is actually a binary star system consisting of Sirius A and Sirius B (invisible to the naked eye).
It's also called the Dog Star, since it's a star in the constellation of Canis Major. It could be perceived as the dog of Orion, following the warrior on the night sky.
Sirius has played an important role in navigation and mythologies throughout human history.

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Location: Kuusamo, Finland
Date&Time: 16th of Feb 2010 20:14(local time UTC+2)
Gear: Nikon D80 & Nikkor 300mm f/4
Settings: | 300mm | f/4 | 20s | ISO 320 |
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