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  2. Okta - Wikipedia

    en.wikipedia.org/wiki/Okta

    Sky conditions are estimated in terms of how many eighths of the sky are covered in cloud, ranging from 0 oktas (completely clear sky) through to 8 oktas (completely overcast). In addition, in the SYNOP code there is an extra cloud cover indicator '9' indicating that the sky is totally obscured (i.e. hidden from view), usually due to dense fog ...

  3. Northern lights forecast for northern US, Midwest this week ...

    www.aol.com/northern-lights-forecast-northern-us...

    The aurora is expected to be bright and visible in multiple northern U.S. states Oct. 3 through Oct. 5 as well as from the lower Midwest to Oregon.

  4. Maps show best areas in U.S. to see northern lights - AOL

    www.aol.com/maps-show-best-areas-u-150216820.html

    Photos show the sky lit ... according to the NOAA Space Weather Prediction Center's aurora forecast. The aurora will be visible over much of Canada and Alaska, but the northern lights can also be ...

  5. Visibility - Wikipedia

    en.wikipedia.org/wiki/Visibility

    The particles scatter light from the sun and the rest of the sky through the line of sight of the observer, thereby decreasing the contrast between the object and the background sky. Particles that are the most effective at reducing visibility (per unit aerosol mass) have diameters in the range of 0.1-1.0 μm. The effect of air molecules on ...

  6. Northern lights forecast: Auroras may be visible across US on ...

    www.aol.com/northern-lights-forecast-auroras-may...

    The forecast storm won't quite have the oomph of the G4-level whopper that came along Oct. 10, but it should still unveil the auroras across the Northern Hemisphere. Where will the auroras be visible?

  7. Clear Sky Chart - Wikipedia

    en.wikipedia.org/wiki/Clear_Sky_Chart

    Clear Sky Charts (called clocks until February 29, 2008) are web graphics which deliver weather forecasts designed specifically for astronomers.They forecast the cloud cover, transparency and astronomical seeing, parameters which are not forecast by civil or aviation forecasts. [1]

  8. Automated airport weather station - Wikipedia

    en.wikipedia.org/wiki/Automated_airport_weather...

    If relative humidity is high (i.e., there is a small difference between the temperature and the dew point), mist or fog is reported, depending on the exact visibility. Fog is reported when visibility is 1/2 mile or less; mist is reported for visibilities greater than 0.5 miles (0.80 km) but less than 7 miles (11 km).

  9. Cloud cover - Wikipedia

    en.wikipedia.org/wiki/Cloud_cover

    Cloud cover (also known as cloudiness, cloudage, or cloud amount) refers to the fraction of the sky obscured by clouds on average when observed from a particular location. [2] Okta is the usual unit for measurement of the cloud cover.