New York, USA
Lat: 40.71°•Lon: -74.01°
ASTRONOMICAL DARK SKY
-4.1° Elevation
True darkness begins; sky is free of atmospheric solar skyglow
First Light (Civil Dawn)11:49 AM
Sunrise12:20 PM
Solar Noon04:59 PM
Sunset09:38 PM
Last Light (Civil Dusk)10:09 PM
True Night (Astro Dusk)11:17 PM
Astronomical Twilight Calculator (-12° to -18°)
-12° to -18° Solar Depression•Bortle Scale Darkness Readiness•Telescope Optical Cooling Window•Limiting Visual Magnitude Tracker
The Deepest Twilight Phase Before Pitch Darkness
Astronomical twilight represents the darkest stage of twilight, occurring when the sun is between 12 and 18 degrees below the horizon. The sky is dark enough for 6th-magnitude stars to be seen with the naked eye, though faint residual skyglow still lingers near the horizon.
Use this time to align telescope equatorial mounts, cool optical primary mirrors, and calibrate autoguiders before true night sets in.
How to Use the Astronomical Twilight Tracker
1
Select your observation site from the menu or input coordinates.
2
Review morning and evening astronomical twilight duration.
3
Calibrate imaging rigs and polar alignment during the -12° to -18° window.
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Frequently Asked Questions
What is astronomical twilight?
Astronomical twilight is the stage of twilight when the sun is between 12 and 18 degrees below the horizon. The sky is very dark, but faint traces of scattered sunlight prevent true optical darkness.
Can you see the Milky Way during astronomical twilight?
Towards the -18° boundary of astronomical twilight, bright sections of the Milky Way core become visible from dark sky locations.
How long does astronomical twilight last?
In mid-latitudes it typically lasts 30 to 45 minutes, but varies significantly depending on latitude and season.
Ready to Use the Astronomical Twilight Tracker?
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