Forecast definition
What is transparency?
Transparency describes how clear the atmosphere is for passing starlight and contrast-heavy sky detail. Good transparency means darker backgrounds and better faint-object contrast. Poor transparency means haze, moisture, smoke, or particulates reduce clarity even when cloud cover is low.
What usually hurts transparency
Humidity and thin haze: Moisture can wash out contrast and dim faint targets.
Smoke or particulates: Wildfire smoke and aerosols can reduce visibility range and detail.
High thin cloud layers: These can scatter light and flatten Milky Way structure.
Transparency vs seeing
Transparency: Sky clarity and contrast.
Seeing: Atmospheric steadiness for sharp detail at magnification.
You can have sharp seeing with mediocre transparency, or clear transparency with unstable seeing. Plan around both signals.
How to apply this tonight
For Milky Way and faint deep-sky targets, stronger transparency is often the priority. For planets at high magnification, seeing can matter more.