StarCast · Milky Way Forecast

Is Tonight Good for Milky Way Photography?

Whether tonight works for Milky Way photography depends on four variables: moon phase, cloud cover, atmospheric transparency, and your Bortle class. StarCast scores all four and gives you a single answer.

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What actually determines Milky Way visibility

The Four Variables StarCast Checks Tonight

A quick glance at a standard weather app won't tell you whether tonight is worth the drive. Cloud cover alone isn't the answer — a perfectly clear sky can still produce a washed-out Milky Way if the moon is up, transparency is poor, or your location has significant light pollution. You need all four variables assessed together.

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Moon Phase: The Biggest Single Factor

A moon more than 40% illuminated will drown out the Milky Way core entirely. The best Milky Way windows fall within 5 days of new moon, when the sky goes fully dark after astronomical twilight. StarCast shows moon phase, rise, and set times so you know exactly how much dark window you have.

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Cloud Cover: Needs to Be Low, Not Zero

Total cloud-free sky isn't required — a broken cloud layer can even add foreground interest. Under 20% cloud cover is the practical threshold for Milky Way core photography. Above 40%, core visibility becomes inconsistent. StarCast penalizes cloud cover progressively in the score.

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Atmospheric Transparency: The Hidden Variable

A clear sky can still have poor transparency from humidity, smoke, or aerosols — and the Milky Way will look dim and washed out even with zero clouds. Post-frontal air after a cold front consistently delivers the best transparency. StarCast factors atmospheric transparency into every score.

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Bortle Class: Your Location's Sky Darkness

The Milky Way core is visible from Bortle 4 and below. In a Bortle 7–8 suburban sky, no amount of good weather fixes light pollution. StarCast pulls your location's Bortle class automatically and factors it into the score — so you know upfront whether your location can even produce a usable result tonight.

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Get Alerted When Tonight Looks Good

StarCast monitors all four variables nightly for your saved locations. When moon phase, cloud cover, and transparency align, you get a push alert before the window opens — not the morning after. Exclusive to the iOS app.

Common Questions

Is tonight good for Milky Way photography?

Check StarCast for your location — it scores moon phase, cloud cover, transparency, and Bortle class together. A score above 70 is a strong Milky Way night. Free on web, push alerts in the iOS app.

What moon phase is needed for Milky Way photography?

New moon or within 5 days of it. A moon above 40% illumination washes out the core. StarCast shows moon phase and the exact dark window for each night so you can plan sessions and travel in advance.

What cloud cover is acceptable for Milky Way photography?

Under 20% for reliable core visibility. Patchy cloud can work for landscape compositions but will interrupt long exposures. StarCast scores cloud cover in bands and combines it with transparency for a realistic picture of what the sky will actually look like.

What Bortle class do I need for Milky Way photography?

Bortle 4 or lower for a visible, photogenic Milky Way core. Bortle 5 is marginal; 6 and above requires significant processing to recover detail. StarCast shows your Bortle class automatically based on your GPS location.

What is LightCast StarCast?

StarCast scores night sky conditions using moon phase, Bortle class, atmospheric transparency, and cloud cover into a single 0–100 score. Push alerts notify you when a strong Milky Way night is forecast. Free on web at lightcastsuite.com/starcast, push notifications in the LightCast iOS app. $2.99/month after a 7-day free trial.