moonrise and moonset
{{Short description|Daily appearance and disappearance of the Moon at the Earth's horizon}}
{{redirect|Moonrise}}
File:Moondrop.jpg sinking behind San Gorgonio Mountain, California, on a midsummer morning]]
Moonrise and moonset are times when the upper limb of the Moon appears above the horizon and disappears below it, respectively. The exact times depend on the lunar phase and declination, as well as the observer's location. As viewed from outside the polar circles, the Moon, like all other celestial objects outside the circumpolar circle, rises from the eastern half of the horizon and sets into the western half{{cite journal |last=|first= |title=Does the Moon rise and set as the Sun rises in the east and... |url=https://www.almanac.com/fact/does-the-moon-rise-and-set-as |journal=Old Farmer's Almanac |language=en |access-date=2021-06-02}} due to Earth's rotation.{{cite web |title=Why does the Sun rise in the east and set in the west? |url=https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question14.html |publisher=Goddard Space Flight Center |website=starchild.gsfc.nasa.gov |access-date=2021-06-02}}
Direction and time
= Direction =
Since Earth rotates eastward, all celestial objects outside the circumpolar circle (including the Sun, Moon, and stars) rise in the east and set in the west for observers outside the polar circles. Seasonal variation means that they sometimes rise in the east-northeast or east-southeast, and sometimes set in the west-southwest or west-northwest.{{cite journal |last=|first= |title=Does the Moon rise and set as the Sun rises in the east and... |url=https://www.almanac.com/fact/does-the-moon-rise-and-set-as |journal=Old Farmer's Almanac |language=en |access-date=2021-06-02}} This north-south variation of the point along the horizon is bookended by two lunar standstills or turnarounds, the directions of which are sometimes depicted in archaeoastronomical constructions.{{cite book|title=Echoes of the Ancient Skies|last=Krupp|first=Ed|page=13|chapter=Marking Time by Moonlight}} It takes 18.6 years for the Moon to traverse this variation viewed from a vantage point on Earth.
= Time =
File:Half moon rising from the back deck (14630153843).jpgs]]
The Moon's position relative to Earth and the Sun determines the moonrise and moonset time. For example, a last quarter rises at midnight and sets at noon.{{Cite web|date=2021-01-01|title=What is a last quarter moon? {{!}} Moon Phases {{!}} EarthSky|url=https://earthsky.org/moon-phases/last-quarter/|access-date=2021-06-02|website=earthsky.org|language=en-US}} A waning gibbous is best seen from late night to early morning.{{Cite web|date=2021-01-01|title=What is a waning gibbous moon? {{!}} Moon Phases {{!}} EarthSky|url=https://earthsky.org/moon-phases/waning-gibbous/|access-date=2021-06-02|website=earthsky.org|language=en-US}} The Moon rises 30 to 70 minutes later each day/night than the day/night before, due to the fact that the Moon moves 13 degrees every day. Hence, the Earth must move 13 degrees after completing one rotation for the Moon to be visible.{{Cite web|last=Scudder|first=Jillian|title=Why Does The Moon Rise Later Each Day?|url=https://www.forbes.com/sites/jillianscudder/2017/06/23/astroquizzical-moon-rise-time/|access-date=2021-06-02|website=Forbes|language=en}}
| class="wikitable"
|+Moonrise/moonset for different moon phases !Lunar phase (illustration as seen from northern hemisphere) !Moonrise{{Efn|Varies slightly. (Same note for "Culmination time (highest point)" and "Moonset".)}} !Culmination time (highest point) !Moonset !Best seen |
| 50x50px New moon
|6 AM |60x60px Noon |6 PM |Not visible unless there is a solar eclipse |
| 50x50px Waxing crescent
|9 AM |60x60px Afternoon |9 PM |Late morning to early evening |
| 50x50px First quarter
|12 PM |60x60px Sunset |12 AM |Early evening to late night |
| 50x50px Waxing gibbous
|3 PM |60x60px Late evening |3 AM |Early evening{{Cite web|date=2021-01-21|title=What is a waxing gibbous moon? {{!}} Moon Phases {{!}} EarthSky|url=https://earthsky.org/moon-phases/waxing-gibbous/|access-date=2021-06-03|website=earthsky.org|language=en-US}} and most of night |
| 50x50px Full moon
|6 PM |60x60px Midnight |6 AM |Sunset to sunrise (all night), a lunar eclipse is then possible |
| 50x50px Waning gibbous
|9 PM |60x60px Predawn |9 AM |
| 50x50px Last quarter
|12 AM |60x60px Sunrise |12 PM |Predawn to post-sunrise |
| 50x50px Waning crescent
|3 AM |60x60px Late morning |3 PM |Predawn to afternoon |
Visual appearance
File:ISS-15_Moonset_above_Coral_Sea.gif
The Moon appears to be larger at moonrise or moonset due to an illusion. This illusion, known as the Moon illusion, is caused by an effect of the brain. There is no definitive explanation for the Moon illusion. However, it is most likely because of how the brain perceives objects at different distances, and/or the distance we expect objects to be from us when they are near the horizon.{{Cite web|last=Preston Dyches|first=By|title=The Moon Illusion: Why Does the Moon Look So Big Sometimes?|url=https://solarsystem.nasa.gov/news/1191/the-moon-illusion-why-does-the-moon-look-so-big-sometimes|access-date=2021-06-03|website=NASA Solar System Exploration}}
The Moon appears to be more yellowish near the horizon. This is for the same reason the Sun and/or sky appears to be orangey-red at sunrise/sunset. When the Moon appears near the horizon, the light coming from it has to pass through more layers of atmosphere. This scatters the blue away, and leaves yellow, orange, and red.{{Cite web|title=What Is the Meaning of a Yellow Moon?|url=https://www.reference.com/science/meaning-yellow-moon-87a729e74b3952f3|access-date=2021-06-03|website=Reference.com|date=4 August 2015 |language=en}} This is also the reason the Moon appears red during a deep partial or total lunar eclipse.{{Cite web|title=What Is a Blood Moon?|url=https://www.timeanddate.com/eclipse/blood-moon.html|access-date=2021-06-03|website=www.timeanddate.com|language=en}}
Notes
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