StarCast · Long Exposure Guide

Best Conditions for Long Exposure Photography

Long exposure photography is the most weather-sensitive genre. Wind, humidity, cloud movement, and moon phase all affect results in ways that standard weather apps don't address. Here's what to check.

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Photography forecast

What Long Exposure Photography Actually Needs

Long exposures accumulate everything that changes during the exposure — wind-blown trees, moving cloud, humidity haze, and ambient light all compound over 20–30 seconds in ways that don't show up in a quick preview. Checking the right variables before shooting saves hours of frustration in the field.

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Wind: The Primary Enemy

Any wind above about 10–12 mph causes visible blur in foreground elements during exposures of 15 seconds or longer — trees, grass, and water all move. Camera shake on a heavy tripod starts above 15 mph. Check sustained wind and gusts separately — DroneCast shows both.

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Humidity and Lens Fogging

When air temperature approaches dew point, moisture condenses on the lens element mid-shoot — a gradual fogging that ruins exposures without obvious warning. Check the dew point depression before overnight shoots. A gap under 5°F between air temperature and dew point means fogging risk is high.

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Moon Phase for Night Long Exposures

For star trails and astrophotography, moon phase determines whether you're working with a dark canvas or a bright one. New moon for dark sky long exposures. Full moon for moonlit landscape long exposures. Both have uses — StarCast shows phase and position for any night.

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Cloud Movement Speed

Slow-moving cloud adds drama to long exposures — streaking across the frame in 30 seconds. Fast-moving cloud in high wind blurs into a flat grey wash. Light to moderate wind at cloud altitude — not at ground level — produces the best cloud movement effects.

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StarCast Push Alerts

StarCast scores the conditions that matter most for night long exposure photography — moon phase, transparency, cloud cover, and humidity. Push alerts when a high-scoring night is forecast. Exclusive to the iOS app.

Common Questions

What are the best conditions for long exposure photography?

Low wind (under 10 mph), low humidity, moon phase matched to your intent (dark for stars, bright for moonlit landscapes), and slow cloud movement. StarCast scores night conditions. DroneCast shows wind and gusts. Free on web, alerts in the iOS app.

What wind speed is too high for long exposure photography?

Above 10–12 mph causes foreground blur in 15+ second exposures. Above 15 mph causes camera shake on a heavy tripod. Check gusts specifically — a 5 mph average with 15 mph gusts will ruin exposures intermittently in an unpredictable pattern.

How do I prevent lens fogging during long exposure shoots?

Check the dew point depression before going out. If air temperature and dew point are within 4°F, fogging is likely. Use a lens warmer or hand warmer near the front element for overnight shoots in humid conditions.

Is overcast good for long exposure photography?

For daytime long exposures — waterfalls, light trails, urban scenes — overcast eliminates harsh shadows and is often ideal. For night long exposures — star trails, astrophotography — clear sky is required. Different use cases, opposite conditions.

What is LightCast StarCast?

StarCast scores night sky conditions using moon phase, Bortle class, transparency, and cloud cover — the key variables for night long exposure photography. Free on web at lightcastsuite.com/starcast, push notifications in the LightCast iOS app. $2.99/month after a 7-day free trial.

Check wind, humidity, and moon phase before your shoot.

Wind · Humidity · Moon phase · Transparency · Cloud cover
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