The Milky Way Doesn't Wait. Neither Should You.
Moon phase. Galactic center altitude. Light pollution. Cloud cover. One wrong variable and you're staring at an empty sky. ShutterTime calculates Milky Way visibility so you know before you go.
Sound familiar?
Full moon ruined everything
Drove 2 hours to a dark sky location, set up at 2am, only to realize the moon rose at midnight and washed out the stars.
"Dark sky" wasn't actually dark
The map said Bortle 4, but there was a city glow on the horizon exactly where the Milky Way core was rising.
Core was below the horizon
Checked moon phase, checked weather, forgot to check if the galactic center would actually be visible that night.
Clear forecast, hazy sky
Weather app said clear, but thin high clouds scattered city light and washed out the faint stars.
What ShutterTime tracks
Moonless Nights
Moon illumination from 0-100%. Lower is better. 0% = perfect. Even a quarter moon washes out the Milky Way.
Milky Way Core Altitude
Galactic center must be above the horizon. Higher = brighter. Core below 15° is dim. Above 30° is spectacular.
Bortle Scale
Light pollution rating from 1-9. We use directional Bortle when core is near horizon. Bortle 4 or lower for serious Milky Way shots.
Astronomical Twilight
True darkness begins when sun is -18° below horizon. Shooting before astronomical darkness? You're wasting frames.
Cloud Cover
Total cloud cover and high cloud specifically. Even thin cirrus scatters city light and kills contrast.
Frequently asked questions
When is the best time to photograph the Milky Way?
The Milky Way core is best photographed during astronomical night (sun below -18°) when the galactic center is above the horizon. In the northern hemisphere, this is typically February through October. ShutterTime calculates exact visibility windows for your location.
What does Bortle scale mean for photography?
Bortle scale measures light pollution from 1 (darkest) to 9 (brightest city center). For Milky Way photography, Bortle 4 or lower is ideal. ShutterTime uses directional Bortle—checking light pollution in the direction of the galactic center, not just overhead.
How do you calculate Milky Way visibility?
We combine galactic center altitude (must be above horizon, higher is better), moon illumination (0% ideal), directional Bortle scale (checking the direction of the core), cloud cover, and astronomical twilight timing. All factors combine into a single visibility score.
How does moon illumination affect astrophotography?
Moon illumination is scored inversely: 0% = perfect (new moon), 100% = worst (full moon). Even a quarter moon (50%) significantly washes out faint stars and the Milky Way. We also factor in moon rise/set times—shooting before moonrise or after moonset gives you dark windows even during brighter moon phases.
Related features
KP index and aurora forecasting
Golden hour and cloud conditions
Blue hour and urban night sky