When is official sunset

As the relative position of the Sun, Moon and Earth changes, differing proportions of the Moon's visible surface are illuminated by the Sun.

The phases of the Moon are specific instances in this process. At this time, the Moon does not appear to be illuminated. At this time 50 per cent of the Moon's visible surface is illuminated.

At this time per cent of the Moon's visible surface is illuminated. The planets which are generally visible to the naked eye are: Mercury, Venus, Mars, Jupiter and Saturn. The rise and set times for these planets is the instant when, under ideal meteorological conditions, with standard refraction of their rays, the planet is coincident with an ideal horizon.

An ideal horizon exists when the surface forming the horizon is at a right angle to the vertical line passing through the observer's position on the Earth. If the terrain surrounding the observer was flat and all at the same height above sea level, the horizon seen by the observer standing on the Earth would approximate the ideal horizon.

The zenith distance is a vertical angle measured from directly overhead, down to the required point. An ideal horizon has a zenith distance of 90 degrees. True north is the direction towards the north pole along the meridian of longitude which passes through the observer's position on the Earth. The vertical angle is the angle measured in a vertical plane, from the horizon to the required point.

Directly overhead would have a vertical angle of 90 degrees. To convert to local time add or subtract the difference between your time zone and UTC, remembering to include any additional offset due to summer time for dates when it is in effect. For each perigee and apogee the distance in kilometres between the centres of the Earth and Moon is given. Perigee and apogee distances are usually accurate to within a few kilometres compared to values calculated with the definitive ELP theory of the lunar orbit; the maximum error over the years through is 12km in perigee distance and 6km at apogee.

Other close-to-maximum apogees and perigees are flagged with a single character, again indicating the nearer phase. Following the flags is the interval between the moment of perigee or apogee and the closest new or full phase; extrema cluster on the shorter intervals, with a smaller bias toward months surrounding the Earth's perihelion in early January. Scan for plus signs to find "photo opportunities" where the Moon is full close to apogee and perigee.

Perihelion is the point in the orbit of a planet, asteroid, or comet at which it is closest to the Sun, while Aphelion is the point in a planet's orbit at which it is furthest from the sun, which is the opposite to Perihelion.

The equinoxes represents either of two times of the year when the Sun crosses the plane of the Earth's equator and day and night are of equal length, while the solstices is either of the two times of the year when the Sun is at its greatest distance from the celestial equator.

Astronomical Definitions. Sunrise and sunset Sunrise Sunrise is defined as the instant in the morning under ideal meteorological conditions, with standard refraction of the Sun's rays, when the upper edge of the sun's disk is coincident with an ideal horizon.

Sunset Sunset is defined as the instant in the evening under ideal meteorological conditions, with standard refraction of the Sun's rays, when the upper edge of the sun's disk is coincident with an ideal horizon. Sun transit time The transit time The transit time of a celestial body refers to the instant that its center crosses an imaginary line in the sky - the observer's meridian - running from north to south.

When the time is displayed, click on the calendar icon below the time to add it directly to your calendar. A custom date box below allows you to select any future date s that you are interested in. Zip Codes or 6 digit Canadian Postal Codes. Example: V3H 1Z7. More Information. As the Earth travels around the Sun in its orbit, the north-south position of the Sun changes over the course of the year due to the changing orientation of the Earth's tilted rotation axes. The dates of maximum tilt of the Earth's equator correspond to the Summer Solstice and Winter Solstice , and the dates of zero tilt to the Spring or Vernal Equinox and Autumnal Equinox.

The first day of winter the winter solstice is the shortest day of the year and the first day of summer the summer solstice is the longest day of the year. During the summer months, the further north you go, the arc of solar travel between sunrise and sunset lengthens and the amount of daylight increases. For regions north of the Arctic Circle at a latitude of It will approach the horizon at midnight, but it will not quite touch it and the Sun will shine all day long. At the latitude of the Arctic Circle, the first day of summer is the only hour day of total daylight.

Further north toward the Pole, the number of hour periods between sunrise and sunset increases. The ultimate long-day occurs at the North Pole where the Sun rises with the Vernal Equinox and finally sets again days later with the Autumnal Equinox. Likewise, during the winter months, for regions north of the Arctic Circle, the sun will set for for at least one full day before rising again.