Sky transparency uses darker blues to indicate excellent transparency and lighter blues and whites to indicate poor transparency.

Astrospheric Professional members will see the smoke sub-component of Transparency when it is strongly impacting the quality of the sky.

The color used to detail smoke on the forecast matches the smoke map overlay legend.

Further details on smoke

Astrospheric's transparency model takes smoke, elevation, and surface pressure into account produce a more accurate forecast. The primary model data comes from the Canadian RDPS with augmentation from NOAA's RAP.

Observing deep sky objects such as faint galaxies and nebulae requires excellent sky transparency. Astronomers evaluate sky transparency with the faintest star visible to the unaided eye. In semi-desertic regions such as Arizona, one can see stars as faint as 6.5-7.2 magnitude. At mid-latitudes and in the more humid eastern regions, most of the time sky transparency is limited to the 5.5-6.5 range in the countryside. Sky transparency also varies with air mass type. With a humid air mass the transparency is reduced significantly. With a continental air mass from the arctic, relatively cold and dry conditions prevail, allowing the sky transparency to be at times be as good as in the semi-desertic regions. Good forecasts of such rare starry evenings will clearly be useful to astronomers.