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Ursa Astronomical Association
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Ursa Astronomical Association

Primary rainbow - 30.7.2021 at 21.54 - 30.7.2021 at 22.00 Paimio Observation number 100102

Visibility V / V

Mikko Peussa, Ursa (Länsi-Suomi)

Today I thought in the afternoon that there could come an evening of rainbows. In Turku, a rainbow was visible when I got out. However, I pondered the situation for a moment and pondered the movement of the rain area and the conditions of the Sunward Sky. I then decided to take a risk and leave 25 km east of Turku for the Paimio fields. Namely, it seemed that I could get to the place without speeding and the last curves of the evening could form there with good luck. On the way, I looked in the rearview mirror that the Sun seemed to be visible right on the horizon just before it was setting and there was a lot of water raining in front, so everything looked good.

I parked my car in a familiar place and watched the sky begin to turn red. Little by little it formed one of the most beautiful rainbows I have photographed. When the Sun is just setting, the rainbow is a high semicircle and in very reddish tones. It’s an almost amazing sight bright and complete.

There was a lot of luck on the trip today, but in the end everything went as I had already thought in Turku :) #bongaa100

Additional information
  • Lightsource of the phenomenon
    • Sunlight
  • Common atmospheric phenomena
    • Secondary rainbow info

      Secondary rainbow or 2nd order rainbow ,is an arc that appears in the colors of the spectrum. The colors are created when light refracts and is reflected in raindrops in the sky. A secondary rainbow is almost always observed with a brighter primary rainbow. The outer color of the secondary rainbow is blue / purple and the inner color is red. The color order of the main rainbow is reversed.

      These two rainbows are located on the opposite side of the sky from the light source that causes them. A typical light source is the Sun, but extremely rarely the Moon can also cause rainbows in Finland. The rainbows of the moon have their own phenomenon identification in Skywarden.

      The main and side rainbows theoretically encircle the spot of the observer's head's shadow, i.e. the so-called antisolar point, as complete rings. Usually, however, their appearance is interrupted by the horizon.

      The econdary arc in theory always occurs with the main rainbow, but sometimes a distant downpour or sunshine can be limited so that the main rainbow is not visible. Another exceptional situation is when the light source is so high that the main rainbow is already below the horizon, but the side rainbow is still above the horizon. The radius of the main rainbow is 42 degrees, which means it falls below the horizon at an altitude of 42 degrees. The radius of the side rainbow is 51 degrees.

      Four rainbows of different orders have been observed. 3rd and 4th order rainbows on the Sun are very rare. Each order rainbow has its own phenomenon identification in Skywarden.

      A bright primary rainbow with fainter secondary rainbow. The colors are reversed in arcs. Image by Aki Taavitsainen


      The red color on the inner edge of the arc reveals that this is a secondary rainbow. Photo by Mirko Lahtinen.

    • Primary rainbow info

      Primary rainbow or 1st order rainbow, is an arc that appears in the colors of the spectrum and is created when light is refracted and reflected in raindrops in the sky. Its outer color is red and its inner color is blue / purple.

      The main rainbow is visible on the opposite side of the sky from the light source that causes it. A typical light source is the Sun, but extremely rarely the Moon can also cause a rainbows. The lunar rainbows have an own category in Skywarden.

      One or more supernumerary bows may occur inside the main rainbow.

      The fully developed main rainbow is at the point of the shadow of the observer's head, i.e. the ring surrounding the so-called antisolar point. Usually the phenomenon is interrupted by the horizon, but from the air, the rainbow can be seen as a perfect circle continuing below the horizon.

      The rainbow gradually turns into a fogbow as the droplet size decreases. The smaller the droplets are, the smaller the rainbow is in size. Rainbows caused by the smaller droplets tend also to be thicker and the white color begins to dominate them. Usually, rainbow and fogbow are clearly separate phenomena, but sometimes intermediate forms can occur.

      Colors can be used as the primary guideline for distinguishing different bow-like phenomena. If the bow shows colors of the spectrum and is not white, it is a rainbow. If, on the other hand, the arc is mainly dominated by white and some of the colors in the spectrum are missing, it is a fogbow.

      Anomalies can sometimes be seen in the appearance of rainbows. They are reported in Skywarden by clicking the box for an anomalous rainbow. One anomaly is a point of discontinuity where the radius of the rainbow changes. The second is the division of the rainbow into two separate arcs.

      Rainbows of four different orders have been observed. A secondary rainbow, i.e. a 2nd order rainbow, occurs often outside the primary rainbow. 3rd and 4th order rainbows are very rare and occur in the direction of the light source (eq. on both sides of the Sun). Each order of rainbows in Skywarden has its own phenomenon identification tag/button.

      Primary and secondary rainbow. Image by Eetu Saarti.

      Primary (on the left) and secondary rainbow (on the right). Image by Vesa Vauhkonen.

      The primary rainbow is often seen as just a band of colors close to the horizon. Photo by Eetu Saarti.

      When the Sun is close to the horizon, the colors of the rainbow turn red. Primary rainbow can be seen on the left side of the picture along with a faint secondary bow on the right. Image by Vesa Vauhkonen.

      Primary rainbow from plane. Also a faint secondary bow is visible. Photo by Jouni Finnilä.

      Primary rainbow with supernumerary bows within the main arc. Photo by Arja-Sisko Airila.

      Strange weather condition with the primary rainbow in the horizon (Sun is at the height of 42 degrees). A faint secondary rainbow is also visible in the sky. Image by Jouni Matula.

      In dense rain, a rainbow may appear against nearby buildings or the forest. Here the main rainbow stands out weakly against the forest behind the apartment building. Photo by Matias Takala. 

      This slightly divided main rainbow (at the top) is probably a sign of flattened water droplets. Image by Jaakko Kuivanen

Comments: 9 pcs
Pekka Parviainen - 31.7.2021 at 01.05 Report this

Isolla riskillä saa joskus isoja kuvia!

Kalle Helenius - 31.7.2021 at 05.27 Report this

Todella hieno!

Jouni Hovi - 31.7.2021 at 10.06 Report this

Hienot kaaret. Pääkaaren vasen laita osuu vielä melko kivasti Turun ursan tornin paikkeille ?

Tero Sipinen - 31.7.2021 at 13.04 Report this

Onnittelut upeista kaarista ja suunnitelman nappionnistumisesta!

Lasse Nurminen - 31.7.2021 at 13.28 Report this

Komea kaari, hyvä nouto!

Timo Kuhmonen - 31.7.2021 at 14.30 Report this

Komean näköinen kaari... Jos on korkealla paikalla ja hyvä näkyvyys horisonttiin, voi kaaren laidat hieman nousta irti horisontista, ennenkuin kaari kokonaan häviää auringon laskiessa horisontin alapuolelle. Kerran olen tuon tilanteen itse nähnyt...

Matias Isosomppi - 1.8.2021 at 12.28 Report this

No nyt on hienoin kuva sateenkaaresta jonka oon koskaan nähnyt omin silmin!! :) Kiitos kuvaajalle tästä!

Mikko Peussa - 1.8.2021 at 16.49 Report this

Kiitos kaikille kommenteista, otan ne nöyränä vastaan. Sateenkaarien kuvaaminen on usein tuuripeliä, mutta niiden ilmaantumista voi myös yrittää ennakoida. Tässäkin auringonkorkeus on jo n. 0 astetta, joten pienestä se on kiinni että tilanne meneekin ohi ja Aurinko ei paista esteettömästi.

Harvemmin se onnistuu niin kuin tällä kertaa. Usein olen yrittänyt ja vain kerran aikaisemmin olen onnistunut jotenkin ennakoimaan myös Paimiossa, mutta yleisemmin kyllä ei onnistu ;-)

Marko Riikonen - 2.8.2021 at 19.05 Report this

Juu, monen muuttujan kyllä pitää osua kohdilleen sateenkaarijahdissa. Mutta rohkeasti yrittämällä sitten joskus onnistaa ja sen paremmalta tuntuu. Mielenkiintoinen seikka muuten ettei tänä vuonna ole nähty ainottakaan heijastussateenkaarta. Viime vuonna niitä tuli Vahtiin inflatoivissa määrin.

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