This week there will be a 'green' moon

Astronomers will have the opportunity to see the blue moon on August 31. This is the last chance for an average phenomenon of almost 3 years to come once.

You can take pictures of the Moon yourself in green
How to use a lens that only filters blue light.

Ms. Hang on Friday, August 31 will not be as green as its name, unless the dust or ash in the atmosphere makes it special. In general, the blue moon is not a name based on color, because the moon will still have the same color as on other occasions.

The term blue moon means a full moon again. For example, in the first half of the 20th century, the blue moon meant the third full moon in a season - winter, summer, autumn or spring - that is, in one season there are four bright moons instead of three.

However, this concept has been misunderstood for many years. Today, we call the second full moon in the month a 'blue moon'.

Normally, the blue moon appears on average every 2.7 years. Sometimes, time appears shorter. For example, in 1999 the blue moon appeared in both January and March (and there was no full moon in February).

The cause of the blue moon is because the calendar months do not match the lunar months. A full moon cycle lasts 29 days, while a calendar day usually takes 30 to 31 days, so there are two full moons occurring in the same calendar month.