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Skywarden,
Ursa Astronomical Association
Kopernikuksentie 1
00130 Helsinki
taivaanvahti(at)ursa.fi

Ursa Astronomical Association

Muu valoilmiö - 19.7.2020 at 18.00 Kangasala Observation number 92187

Visibility IV / V

Jari Luomanen, Ursa (Länsi-Suomi)

Such a summer fun. I went diving in Kangasala in Ukkijärvi, and there seems to be blue-green algae or some other algae as a fairly flat flock of algal particles floating in water.

Since the situation was in a fun way reminiscent of winter ice mist (without being there anyway), I decided to look at what kind of optics can be observed in the situation.

The figure shows the light density caused by the Caustic Zones on the surface, i.e. the undulation, and the colors produced by chromatic aberration. This beam was visible when the beam of view was at approximately right angles to the beam projected from the surface. But it also required that the line of sight be in approximately the same direction as the Caustic zone on the surface itself, which is always in motion with the undulation. So the phenomenon is shaky and momentary, but extraordinarily beautiful.

The algae particles thus scatter the light accumulated as a "beam" due to the shape of the air-water interface, but this is not about the algae itself contributing to the phenomenon, e.g. by refracting the light inside or through diffraction. They only act as a surface on which the optical phenomena caused by the Caustic Zones (i.e., the condensation of light into a “ray” and the scattering of light into the colors of the rainbow, i.e., chromatic aberration) can be projected. That is why I marked this as another phenomenon and not as an algal phenomenon.

The light densities of the slightly wavy water surface shapes are easy to detect on the shores of a clear-water lake or sea, as they appear as ever-living patterns on the bottom. In this case, it was nice that they were so clearly projected onto algal particles floating in clear water and thus visible as such colorful rays when viewed from a suitable direction.

Pike sends greetings. Personally, at least I don’t know if I got any symptoms of cyanobacterial poisoning. ;)

Joy and optics for all summer! :)


Additional information
  • Lightsource of the phenomenon
    • Sunlight
  • Rare atmospheric phenomena
    • Other atmospheric phenomenon info

      Muu valoilmiö -luokassa voit raportoida sellaisia harvinaisia ilmakehän optisia ilmiöitä, jotka eivät kuulu tämän sivuston muihin ilmiöluokkiin, ja jotka ovat omassa lajissaan komeita. Muun valoilmiön alla ei ole tarkoitus raportoida niitä erittäin yleisiä valoilmiöitä, joita ei kerätä Taivaanvahtiin, kuten tavanomaisia pilvisäteitä.

      Valetieteellisiä ilmiöitä tai nk. ufo-raportteja ei kerätä tälle sivustolle. Ufo-raportilla tarkoitetaan tilannetta, jossa ilmiön näkijä on jo valmiiksi vakuuttunut siitä, että hänen näkemänsä kohde on varmasti luonnontieteellisin keinoin selittämätön tai on selitettävissä vain yliluonnollisesti tai vieraan sivilisaation vierailulla.

      Taivaanvahtiin voi raportoida tunnistamattomia komeita taivaanilmiöitä, mikäli kyse on asiallisesta tiedustelusta ja havainnosta.

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