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Three possible photographic detections of the natural fifth order rainbow from Germany

In 2014, Harald Edens reported ten cases of photographically detected natural quinary rainbows, recorded during 2009-2013 in New Mexico, USA, at altitudes of 1.8-3.2 km. These and some newer observations can also be found on his website.

So far, no reports from other locations have been published. In the German observers’ network, we analyzed many candidate photographs showing bright primary and secondary rainbows, but from most of them no reliable traces of quinary rainbows could be extracted. Such analyses are not easy, as the quinary signal is weak compared to the neighboring secondary rainbow, and processing methods such as unsharp masking can cause a leakage of colors into Alexander’s dark band. Furthermore, the processing operator will experience disturbing afterimage issues from the intense renditions of the primary and secondary on the screen after a couple of minutes.

Despite these difficulties, we now believe that we have identified three cases of genuine quinary rainbows. In cases 1 and 3, the quinary could be extracted from several photographs. Nonetheless, in order to keep this blogpost brief, we restricted ourselves to show only one image (or the results from one polarization series in case 1) per observation. We chose a straightforward processing method (= only increasing contrast and saturation, no local filtering such as unsharp masks) similar to the one applied by Harald Edens to allow for an easier comparison with his results. Alternative processing routes will be presented at a later stage.

1) April 22nd, 2012, near Göttingen, Germany (51° 31’ N, 9° 58’ E, altitude 250 m), 19:16 CEST, sun elevation 10.2°, photographed by Frank Killich after a moderate shower

The original intention of Frank Killich was to use the primary and secondary rainbows as test objects for a home-built photopolarimetric setup made from a Canon 20D camera and a linear polarizer precisely rotatable by a stepper motor. By recording four successive images at polarizer positions of 0°, 45°, 90° and 135° with respect to the vertical, it is possible to reconstruct the first three components of the Stokes vector for each viewing direction (pixel coordinates) and color channel (red, green, blue) individually. These images can be numerically combined to reconstruct the unpolarized intensity (= the ordinary photographic result without a polarizer) and, moreover, the linearly polarized portion of the recorded light distribution (= the total intensity with the unpolarized background removed for each pixel). In the case of rainbows, this corresponds effectively to a subtraction of the radial (weak) component from the azimuthal (strong) polarization component equally all along the visible part of the circumference. As known from theory, also the quinary will be easier to detect in such a polarization contrast image.

Unpolarized intensity as calculated from the original images, f = 22 mm:

2012_04_22_3541_S0

Unpolarized intensity, increased saturation and contrast:

2012_04_22_3541_S0_b

Linearly polarized portion as calculated from the original images:

2012_04_22_3541_LPA

Linearly polarized portion, increased saturation and contrast:

2012_04_22_3541_LPA_b

The expected broad bands of green and blue are clearly visible in the processed linearly polarized portion picture, and might be slightly visible also in the unpolarized intensity.

The other two photographic observations were carried out without any polarizers, i.e. only the unpolarized intensity information is available in these cases.

2) March 20th, 2013, near Pforzheim, Germany (48° 56’ N, 8° 36’ E, altitude 312 m), 16:21 CET, sun elevation 21.1°, photographed by Michael Großmann after an intense shower

Original (Canon EOS 450D, f = 22 mm):

2013_03_20_05

Increased saturation and contrast:

2013_03_20_05_b

A slight green/blue hue is visible inside the secondary at and slightly above the horizon.

3) May 15th, 2016, Mt. Zschirnstein, Germany (50° 51’ N, 14° 11’ E, altitude 560 m), 19:57 CEST, sun elevation 6.2°, photographed by Alexander Haußmann after a moderate shower

A description of this observation (without discussing the quinary rainbow) can be found here. The images shown here are cropped from a fisheye photograph.

Original (Pentax K-5, f= 17 mm, cropped):

2016_05_15_IMGP6762_A

Increased saturation and contrast:

2016_05_15_IMGP6762_A_b2

Again, a slight green/blue hue appears close to the horizon.

At this point it is of course not possible to draw any statistical conclusions about the frequency of detectable quinary rainbows. However, it seems worthwile that every rainbow observer re-examines his photographical treasure trove for previously overlooked rarities, even if no polarizer enhancement was involved during photographing.

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Twinned rainbow from Russia

OLYMPUS DIGITAL CAMERA

Twinned rainbow in Siberia, Russia in Original and with unsharp mask. Photo: Ivanna Dark

In June 21, 2016 Ivanna Dark observed Yurga, Kemerovo region in Western Siberia, Russia an clear twinned rainbow: “At 19:45 local time (UTC + 7) began to fall to the ground a few large drops of very weak rain. I decided to look at the rainbow, because I know that it will appear in the presence of the sun. Imagine my surprise when I saw that the rainbow has a certain strangeness. It was not a Supernumerary Rainbows, but seen clearly, that the top part split into equal pieces. Later I found out the name of this phenomenon – Twinned Rainbow. Although the rainbow was very faint and lasted about two minutes, it did not stop to notice the duality of top.”

Moonbow with Alexander’s dark band

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On July 31, 2015 was a “blue moon” (second full moon in a month). The weather forecast for that night in Spain was storms and heavy rains. I was travelling from Madrid airport to the north of Spain. The first atmospheric phenomenon was a 22 degree halo that I photographed in the rural areas of Castilla. Then the storms began and the blue moon disappeared. At 5am I was already at my home in Villaverde, Leon. It was raining all night but then only for a few minutes the moon appeared again on the wester horizon and produced this double moonbow with Alexander’s dark band.

I created also a short timelapse video of a second  moonbow , late that night, just before dawn. Pictures taken with Nikon D5300, Nikkor fisheye 10,5 mm, f:2,8, ISO 400, 20 sec exposure.

Author: Roberto Porto, Spain

Niagara Falls Rainbow

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After being up at Niagara Falls back in 14 I had to come back for more and wanted to be there when the lights on the Canadian side light up the falls. The night we arrived the light were turned up and got to see some amazing rainbows. The lights would change color and it was a sight to see a rainbow being different colors along its length. In addition to the floodlight bows I also got nice rainbows from natural sunlight and using the super wide angle field of view with my GoPro camera I got nice full circle rainbows. For anyone who is a waterfall or rainbow chaser. Niagara Falls is the place to go and falls are BEST on the Canadian side and this is the perfect bucket list item.

Author: Michael Ellestad, Ohio, USA

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 (12).

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

“Spektrodrom” – A Laboratory of Rainbow

The simulation of rainbows of many orders with hanging or standing water drops and laser light is straightforward, but often unrealistic due to deformation of the drops. Therefore, a modern version of Billet’s experiments was designed, which uses a laminar cylindrical flow of water, and white light by just a few pixels of a video projector. It is surrounded by a circular projection screen. Using slightly skewed rays, which are therefore “climbing” up the cylindrical beam of water and exiting from it in proportion to the number of partial reflections, is able to produce a simultaneous display of the first six rainbow orders in white light.

The 2nd and 3rd order.

The 1st, 4th and 5th order.

The first 4 orders.

Both 1st and 2nd orders.

Both 3rd and 4th orders.

The first six orders.

Animation about the different refraction angle beetween salty water and fresh water.

Author: Michael Großmann, Kämpfelbach, Germany

Supernumeraries on primary and secondary rainbow

In the evening of July 3 2013, Wolfgang Hinz observed a double rainbow at Schwarzenberg in Saxony, Germany, which showed an unusually high number of supernumerary bows (1234). This points out that the rainbow was caused by very small raindrops. As the two bows turned fainter and became incomplete because of being partially shadowed by clouds, Wolfgang Hinz could also see supernumeraries outside the secondary rainbow with the naked eye (12) for the first time in his 30-years-history of observing atmospheric phenomena!

At the same time, but about 200 kilometers away in Thuringia, I also observed a rainbow with a similarly high number of supernumeraries inside the primary bow (1234) in a rain shower that moved away. But in this case, there were no supernumeraries outside the secondary bow.

Zero Order Glow

When rain is falling with the setting sun behind it, there sometimes appears a golden or deep red glow in shape of a semicircle around the sun. Literature calls this glow “Zero Order Glow”. The name means that this glow is a zero order rainbow. This is because the light is not reflected within the raindrops once or twice, as it is the case in primary and secondary rainbows. In the case of a zero order glow, the light passes through the raindrops without being reflected, leaving them only a bit deviated. So there is no bow-shaped concentration of light, and the zero order glow appears in form of a diffuse shining area around the sun.

In normal cases, the phenomenon is visible only above the horizon. But when this photographs (23) was taken, a fine drizzle fell into the valley from a very low layer of clouds, causing also a glow beneath the horizon. Due to the low sun elevation and the long way the sunlight had to travel through the atmosphere, together with the additional light diffraction on the small drizzle particles, there is only the red light visible.

Author: Claudia Hinz, Wendelstein (1835m), Germany

Extremely red rainbow

This red rainbow appeared while the sun was setting and persisted even some minutes after sunset. At that time it was rather dusky already, and the glowing tops of the distant Alps appeared rather unreal. A short time later, a red rainbow appeared, showing an intense red colour which in this intensity I had never seen before. It showed its maximum intensity about 5 minutes after the calculative sunset, but the sun had already sunk behind a mountain some time before. After only a few minutes, rainbow and afterglow faded away simultaneously. The picture is a panorama made of 4 portrait frames with the single frames slightly underexposed, but not processed. The pictures are taken at ISO 800, shutter time 1/40 sec, f/4,5, and a polarizer was used.

At such low sun elevations, all short waved colours of the light are scattered away on the long way through the atmosphere, leaving only the long waved red light behind. This red light reaches the observer´s eyes as alpenglow and as a red rainbow. As, due to their altitude, the clouds (in this case altocumulus in about 3.000 metres) receive sunlight even longer than the ground, in rare cases a rainbow can even be visible after sunset.