A clear sky can produce an unsteady telescope view. Two useful words describe different problems: transparency concerns how much light gets through the atmosphere, while seeing concerns how steadily an image holds its shape.
Decide which matters for the target
Haze or thin cloud reduces contrast and can make a faint galaxy difficult to see. Turbulent air can make a planet or the Moon's edge shimmer even when the sky looks clear. A night can be useful for wide-field clusters while disappointing at high magnification.
NightSky's weather assessment uses available forecast fields such as cloud, wind and humidity. It is not a specialised seeing forecast. A high score does not promise fine planetary detail, and a lower faint-object score may still leave a useful bright-Moon session.
Check the view before adding power
Begin with a low-power eyepiece and focus carefully. If the image ripples, try a lower magnification and watch for brief steady moments. A target low over the horizon is viewed through more atmosphere than one high in the sky. Local heat from a roof or paved surface can also spoil a particular line of sight.
Give the instrument the settling time recommended by its maker. If every object is fuzzy, also check for dew, accidental focus changes and unstable support. Those are equipment problems rather than proof of poor seeing. Keep separate notes for cloud, sky clarity and image steadiness. That distinction makes later comparisons useful and prevents an ordinary cloud percentage from becoming a promise it was never designed to make.
Sources and review
Reviewed October 22, 2026 by PiSpace Sky editorial. Date-sensitive details can change.