Terminator Calculator
Terminator Target Log
LIVE TRACKING
Moon Phase Today
Moon Phase Tracking and Astronomy Data
Moon Phase Today
Moon Phase Tracking and Astronomy Data
The Science of the Shadow
The Lunar Terminator is the dividing line between day and night on the Moon. It is the absolute best place to observe lunar features because the low angle of the sun casts long, dramatic shadows that reveal the 3D depth of craters and mountains.
Can you outrun the sunset?
Yes! The terminator line moves across the lunar surface at roughly 9.6 mph (15.4 km/h) at the equator. A moderately fit human could literally run fast enough to stay in the sunlight forever on the Moon.
Extreme Temperature Shock
Crossing the terminator line is dangerous. In the sunlight, the temperature is boiling at 250°F (120°C). Just a few feet away in the shadow, it drops instantly to -208°F (-130°C).
The “Golden Handle”
Because the Moon has no atmosphere to scatter light, mountain peaks on the dark side can catch sunlight before the ground below them. These are called “Sunrise Rays” and create stunning optical effects.
The Photographer’s Rule
Never photograph the Full Moon if you want detail! A Full Moon is “flat” light (like a camera flash). Always target the **Waxing or Waning phases** and aim your lens directly at the terminator line.
Pro Tip
Look for the “Lunar X”: A famous optical illusion created by the rims of the craters Blanchinus, La Caille, and Purbach. It is only visible for about 4 hours during the First Quarter phase. Use the calculator above to find the next First Quarter!
Why does the Terminator line move right to left?
In the Northern Hemisphere, the moon waxes (grows) from right to left. Sunlight fills in from the West (right side of the moon) towards the East. However, if you were viewing from Australia (Southern Hemisphere), the process would look reversed!
What is the difference between the Terminator and the Limb?
The Terminator is the shadow line created by the sunrise or sunset on the Moon. The Limb is the physical edge of the Moon against the blackness of space. The Limb is always round; the Terminator changes shape constantly.
Why is the Terminator line fuzzy?
Actually, viewed through a telescope, the line is jagged! This roughness is caused by the Moon’s rugged terrain—mountains, valleys, and crater rims blocking the sunlight. It is not smooth like a ball bearing because the Moon is covered in geology.