ISC-11 // Astronomy
Sun & Moon Times
Sunrise, sunset, twilight, moonrise, moonset and the Moon's phase for any ground station, worked out from the positions of the Sun and Moon as seen from that exact spot.
The day at a glance
Altitude of the Sun and Moon over 24 hours. The background shades from night through twilight to daylight. Hover for positions.
Upcoming Moon phases
The next eight principal phases after the selected date.
Month
Select a day to show it above. Illumination is at local noon.
How this is calculated
Sun and Moon positions come from Astronomy Engine (Don Cross, MIT licence), which follows the VSOP87 and ELP/MPP02-based lunar theories to well under an arcminute. Positions are topocentric: they are computed for the station itself, which matters for the Moon, whose parallax shifts it by up to a degree.
Rise and set times are found by stepping through the local day every 10 minutes and refining each horizon crossing by bisection. Rising and setting mean the upper limb touching the horizon, allowing 34′ of refraction and the body's actual apparent radius on that day. Solar noon and Moon transit are the moments of highest altitude. Twilight begins or ends when the Sun's centre is 6°, 12° or 18° below the horizon.
Refraction near the horizon varies with the weather, so real rise and set times can differ by a minute or so. Leave the dip option off unless the site genuinely looks down on a lower horizon; hills or buildings around a site cancel it out.