Reflected Sunlight Dewbow

Reflected Sunlight Dewbow. Photos: Jérémie Gaillard

On August 19, 2010, Jérémie Gaillard made an interesting discovery when looking at the surface of the lake Etang de l´Alleu which is located in the French community of Saint-Arnoult-en-Yvelines. The water was covered with pollen, on which droplets of dew had formed. In these droplets two colourful rainbows were visible. Dewbows can be understood as the lower part of a rainbow projected onto a horizontal plane. When a dewbow is fully developed, a semi-circle which opens towards the sides should be visible, the apex of which is situated at the lower end of the observer´s shadow. Equivalent to normal rainbows, primary and secondary dewbow should run parallely, but in Jérémie Gaillard´s observation they did not.

Instead, the second colourful bow fragment is a reflected sunlight dewbow. The surface of the water acts as a large mirror reflecting the sun. The reflected image of the sun now acts as a second source of light, which is situated as far below the horizon as the sun is above it. (angle of incidence = emergent angle). So the antisolar point for the reflection of the sun is above the horizon. This reflected antisolar point, which is located the double of the real sun´s elevation above the antisolar point, is the centre of the two rainbow circles for the reflected sunlight. So the additional rainbows are displaced upwards by the double sun elevation compared to the primary and secondary rainbow, making a rather unfamiliar appearance in the open nature.

Author: Claudia Hinz

Red Sky Glow by reflected Dawning

In the morning of January 24, 2015, I noticed that the sky was covered with low clouds, except for a small gap right above the southeastern horizon, where the sun would rise about 20 minutes later. So I expected a wonderful dawning, but nothing happened. But at 8.10 a. m., I noticed a strange red light coming from the west. When looking out of the southward window, I saw the western and southwestern sky glowing in a dark red colour.

During the following minutes, the red glow slowly extended eastward and became more and more intense. At last it was so intense that even the ground took this colour, giving that morning a quite eerie mood. In the picture taken in northeasterly direction (2) you can see this reflex on the ground, especially on the gravel path and the pedestrian crossing at the lower left. And the picture also shows that towards the east the low clouds still had their normal dark grey colour. In the southeast, no trace of a normal dawning was visible, but higher in the sky there was also this strange red glow from above. (3) This is vice versa to the normal course of a dawning, where the red colour spreads from east to west.

During the next 5 minutes, the light from above became even brighter and turned into a more orange colour (4). At 8.25 a. m., just before sunrise, a bit of sunlight reached the lower surface of the low cloud layer, but it was by far not as intense as the glow coming from above (5).

Author: Peter Krämer, Bochum, Germany

Reflected pillar & rays in windows

On April 9th, 2014, Uwe Bachmann observed a pillar of light, produced by sunlight falling onto the building of the European Central Bank (EZB) in Frankfurt. He was observing from the German Weather Service’s (DWD) headquarters in Offenbach, i.e. from a distance of 3 kilometers.

For his first photo taken at 6.17 UTC, the sun was at an elevation of 13.9° and at an azimuth of 94.8°. The upward beam of light is thought to be produced by reflection from the building’s front, which is at an angle of 9° to the vertical, with scattering from aerosol producing the luminous pillar.

With the rising of the sun and the changing of its azimuth, this pillar is “cut down” subsequently. The second photo shows the situation at 06.35 UTC for a solar elevation 16.8° and an azimuth of 98.4°. The skewness of the reflected beam of light at an angle of 45° is evident.

The last photo taken at 06.52 UTC for a solar elevation 19.5° and an azimuth of 101.8° shows the beam being reflected almost at a right angle. Here, the azimuth of the sun is almost coincident with the observer’s.

More pictures: 1 – 2 – 3 – 4

Author: Michael Großmann,Kämpfelbach & Uwe Bachmann DWD, Offenbach, Germany

Corona around reflection of Sun

In the evening of June 6, 2014, a reflection of the sun appeared in an inclined window pane of the pyramid-shaped restaurant building on the top of Mt. Zugspitze, while shreds of cumulus clouds coming from the valley passed by. In these shreds not only the shadow of the top of the building was visible from time to time, but there also appeared a distinct corona around the reflection of the sun.

Author: Claudia Hinz

Fraunhofer lines in rainbow ?

Fraunhofer lines are dark lines in the sun’s spectrum. They are caused by resonant atomic absorption of the sun’s thermal continuum radiation by photospheric gases.

The lines provide clues to the chemical composition of the solar atmosphere, as well as its physical conditions like temperature, pressure, magnetic fields etc.

My rainbow photography dated 11.Oct.2013 showed some greyish bands in the yellow.

Are they traces of the strongest Fraunhofer lines or artifacts of the camera’s sensor being unable to profile intermediate colors?
Is it possible at all to obtain spectral lines in nature without a prism or grating?

Author: Michael Großmann, Kämpfelbach, Germany

Third and Fourth Order rainbow in Russia

Sergei Antipov observed on June 22, 2013 in the Vladimir region, Russia (100km from Nizhny Novgorod city) beside a primary and secondary rainbow, the rainbow third and fourth order too.

Time: 14:00 (UTC + 4h)

Weather condition:
+20.1ºС, relative humidity 98%
atmospheric pressure 747mmHg (normal at 82m is 752-753mmHg)
Min/Max: +14.0º / +20.8º
Rain during the day: 3 times, thunder-storm and heavy rain.
wind: in the morning northern, in the afternoon and in the evening eastern
Light breeze, 1 – 3 meter per second, gusts were not stronger than 10 meters per second

Photo time with 1st and 2nd order rainbows: 19:37 (+4)
Photo time with 3rd and 4th order rainbows: 19:47 (+4) (1st, 2nd were visible too)
sunset: 21:52 (+4), azimuth 315º
sun azimuth @ 19:47 291º, height 15º

In late afternoon there were black clouds that came from the east (usually cumulonimbus comes from the west). Cumulonimbus covered almost all the sky and although it was not raining, there was a bright primary and a good secondary rainbow. The sun was covered by clouds. You can see that on a roof of the house there is no shadow. But two rainbows were visible and were bright!
10 minutes later there was bright sunshine (you can see a shadow on a roof of the house).
The sun appeared at 19:47. Till this time the sun was hidden).
The rain began at about 19:45. 3rd and 4th rainbows are photographed from under an umbrella.
But the rain was very weak. From the sky rare droplets of water fell.
Even the roof of the house remained dry (but with traces of drops).
At this moment the rare rainbow also was observed.
The heavy rain began much later (>20:00)
The sun became covered by a cloud, and the first rainbow gradually disappeared.

Chronology:

• Good weather (the last hour)
• clouds (from the East) and sun (in the west) ~ 19:00
• dark clouds (sky half) and sun ~ 19:20
• gray clouds (3/4 of sky) and NO sun, No rain (Or very slight rain that I didn’t feel it) = 19:37
• Beginning of observation of the first rainbow (without rain and without sunshine) within a few minutes there was a sunshine
• very dark clouds (more, than 3/4 of sky) and bright sunshine (the sun shone from beneath a cloud border)
• Slight rain (isolated droplets)
• photo of observation of 3rd rainbow at 19:47

The panorama is made of two photos with an interval 10 minutes; photos are made from different places (about 10 meters). The lens has a bad distortion towards the edge…

Weather that evening was unusual. Cumulonimbus clouds came from the East (usually they come from the West). Therefore I well remember that evening.

The Quality of the original photo is not really good therefore all colors of a rainbow are visible only on “psuedo-HDR” processing (combination of 15 files from one raw with different parameters of brightness, contrast, an exposition and a saturation (1 – 2).

From one file it is difficult to receive such picture: red color smoothly passes in green color without orange, without the yellow (edited photo).

Each method of processing has the merits and demerits. For example, processing in the LAB mode very well showed 4th order, but a bad color rendition of 3rd order rainbow.
Processing with imaginary hdr shows 4th worse, but much better color at 3rd order rainbow.

This sketch show the most interesting moment.

My 3rd and 4th order rainbows are very similar to rainbows of Michael Theusner: strictly at level (at height) the sun, rainbows seem vertical. From below and from above, rainbows sharply are rounded. This effect (I think) is explained by that rainbows have the best brightness at sun height. Very much reminds ice halo: at it too (very often) the brightest piece at the left and to the right of the sun.

Nicolas Lefaudeux invented a search method 3rd order rainbow. His method is outlined here and given in more detail.

I used an other (own) method. It is a Processing scheme to find a rainbow in the photo from one 16bit tiff file from RAW (in LAB mode in Photoshop):
RAW file -> Lightroom3 -> zeroed preset -> 16bit tiff file -> Photoshop -> LABmode

I don’t think that my Processing scheme can be suitable for all photos of other photographers.
But, this method very well shows rainbows in my photo (Frankly speaking, I couldn’t repeat Nikolos’s method – I am the novice user of photoshop 🙂 ).
For faint Rainbows it is necessary to work with layers of A and B (in LAB mode).
You can see a layer “L” on this picture and here the result of work with use of my method.

Author: Sergei Antipov, Russia

Related Post: Natural tertiary rainbow 3rd order

Spider silk glitter path

While taking a walk, I noticed a field that was covered with fine spider silks. The sun was rather low (about 10°) and made a kind of lower light pillar appear in the silks. When I took a closer look, I could also see concentric circles of light with the sun in their centre.(2)

These circles are caused by the perspective and the angle in which the light strikes the surface of the spider silks. The light gets reflected best to the observer when the reflecting surface is positioned at an angle of 90° to the source of light. A similar effect can be observed when a street lamp shines throug wet branches of a tree.(3)(4)

The “lower light pillar” can be seen better because the sun as the source of light shines vertically down onto the field and all spider silks in this direction reflect the light towards the observer.

Place : Kämpfelbach, Germany
Time : 01 November 2011
DSLR Camera : Canon EOS 450d
Exposure : 1/60 sec, f/22mm, F/10, ISO 100

Author: Michael Großmann, Kämpfelbach, Germany

Dewbow

Dew bows are a kind of rainbows. The difference lies in the plane of projection and in the fact that static droplets are reflecting the refracted light back into the eyes of the observer. The rainbow cone resulting, the apex of which is the oberver´s eye, is cut by the plane (the field). The result is a hyperbola, but for our eyes, there is always a circle!.

The first nights in October were rather cold, so that a lot of dew could form in the fields.

I knew that the following days were ideal for looking for the dew bow.

The main problem while observing dew bows is the brightness of the field. A polarization filter makes the dew bow contrast better from the background. (2)

An even better idea was filming the dew bow while driving along the farm track. This makes it contrast even more clearly.

Place : Neulingen, Germany
Time : 02 October 2011
DSLR Camera : Canon EOS 450d
Exposure : 1/25 sec, f/10mm, F/7, ISO 100

Author: Michael Großmann, Kämpfelbach, Germany

Rings of Quételet

Rings of Quételet are caused by rays of light which had been scattered by particles of dirt on a window pane and then were reflected from the rear side of the pane, interfering with rays having been reflected from the front side of the pane and then having been scattered by the same dirt particles.

The light source itself forms a white circle being surrounded by colourful rings which are caused by interferences.

These rings always begin with a blue one right outside the white circle and end up with a red one on the other side, away from the circle, no matter if the secuence begins in the centre of the pane or on its rim.

Place : Fehraltorf, Switzerland
Time : 24 August 2011
Digital Camera : Canon EOS 450D
Exposure time : 1/2500 sec , f/9 ,Focus length 22mm, ISO 100

Author: Michael Großmann, Kämpfelbach, Germany

A single water drop

A slight-projector and a singel water drop shows a lot of bows. Here you can see the primary, secondary and tertiary bow.

The distance between the water drop an the projection backside (white paper) is 30 mm, waterdrop an light source has an diameter of 2 mm.

Photo taken on 28.07.2011 on my desktop 🙂

Author: Michael Großmann, Kämpfelbach, Germany