Super Blue Blood Moon – Once in a Blue Moon

Check the moon in this evening’s clear skies (29 January 2018) because the forecast for the rest of the week is for cloud cover.

The 31 January 2018 will see the coincidence of three special types of moon:

  • Blue moon – The second full moon in a month (the last was 2 January 2018).
  • Super moon – The moon is near its perigee (closest part of its elliptical orbit to Earth). The result is a moon, which appears 14% larger and 30% brighter than normal.
  • Blood moon – In the western US through to Eastern Asia there will be an eclipse of the moon (the Earth will block the sun’s light from landing on the moon.) As the sunlight passes through the earths atmosphere and bends it casts a reddish shadow on the moon as much of the blue frequencies are absorbed/scattered by the Earth’s atmosphere– hence the Blood Moon, and our blue sky.

The Lunar eclipse is forecast to last about an hour and 15 minutes. As the Earth’s atmosphere scatters more blue light than red, causing observers from Earth to see a rusty-red coloured moon. The phenomenon is called ‘Rayleigh’s scattering’. It is the same scattering phenomena, which gives us the blue sky (i.e. scattering of the light down towards the Earth’s surface). The scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the blue colour of the sky and the yellow/orange (i.e. not white) tone of the sun, which is more noticeable while the sun is low in the sky at dawn and dusk.

The irregular orbit of the moon is the major contributor to the fluctuations in the tidal heights and the timing of tides. Last weekend the Equinox team attended the RYA instructors and principals’ conference where Ivan Haigh (Southampton University Oceanographer) explained the different drivers in the fluctuation of tidal heights.

We will be running a series of workshops throughout the year, focusing on interesting sailing related subjects, including tides. Look out for further details to follow.

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