Antoniadi scale

The Antoniadi scale is a system used by amateur astronomers to categorise the weather conditions when viewing the stars at night.

Living most of his life in France, he spent his time viewing Mars from Camille Flammarion's observatory.

Now the scale considered as the metric system of astronomical seeing, being used as a default measurement all over the world.

The actual definitions are as follows: Note that the scale is usually indicated by use of a Roman numeral or an ordinary number.

[2] Astronomers have devised several methods for defining the quality of seeing apart from the Antoniadi scale, including: