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Questions tagged [moon-phases]

For questions about the various phases on the Moon as observed from the Earth, also known as waxing and waning.

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How many times does the moon rise between two new moons?

How many times does the moon rise between two new moons? This might be a silly question not meeting the standards here, in that case I will delete it. I have tried to write a program using perl, but ...
Gyro Gearloose's user avatar
1 vote
1 answer
104 views

Ancient adjudication of the new moon from witness testimony

The ancient method of certifying the new moon in the Land of Israel in ancient times is described in Mishnah Rosh Hashanah 2:6. Witnesses would come to Jerusalem and testify before the Sanhedrin that ...
wberry's user avatar
  • 349
2 votes
2 answers
100 views

Determining Vernal Equinox by observation

Medieval society determined the date of Easter (or Passover) relative to the Full (or New) Moon on or after the (day of the) Vernal Equinox, where the state of the Moon was observed rather than ...
Mark Morgan Lloyd's user avatar
1 vote
1 answer
75 views

Are the NASA Dial-A-Moon frames rendered as seen from the north and south poles?

I would like to rotate the images to match the view from my window and to do this I need to know the location for which the original frames are rendered. The relevant description on the page https://...
Reginald's user avatar
1 vote
1 answer
141 views

sideways crescent moon but also no moon somewhere else?

I live in Sumter, South Carolina and the moon looked like a crescent moon but sideways like a bowl. But when I told my friend to look at the moon they couldn't find it and they live in Buffalo, New ...
Cakebandit06's user avatar
6 votes
1 answer
1k views

How can the new moon set before the sun, as will happen in some locales on November 13, 2023?

I have somewhat of an interest in sighting the new moon. I recently heard a lecture by someone who had written a program to provide the conditions for the first new moon sighting for any location for ...
Michael Appel's user avatar
3 votes
1 answer
128 views

How much does the eccentricity of EARTH'S orbit effect the length of the synodical lunar month?

Usually, only the eccentricity of Moon's orbit is used as an explanation for the varying length of the lunar month. But Earth's orbit's eccentricity should also contribute to that. How much does it ...
George Lee's user avatar
5 votes
1 answer
271 views

Will Lunar Months be the same length Millions of Years in the Future?

If I remember correctly, the amount of time it takes for the moon to rotate around Earth is getting longer over time. Is this true, and if so or the opposite is true and a lunar month is getting ...
Dromeoraptor pennato's user avatar
1 vote
0 answers
116 views

Is this "lunar theorem" known?

About a month ago I concieved the following "lunar theorem": Whenever the moon is visible at dusk (strictly speaking, to an equatorial observer, if eg. the planet is very large compared to ...
AlgebraicsAnonymous's user avatar
4 votes
2 answers
566 views

What does the moon's phases look like from the Equator?

I recently found out that the moon's appearance changes based on one's latitude, and while googling for more information I found conflicting images about what the moon's phases look like from the ...
Wimateeka's user avatar
  • 141
6 votes
3 answers
315 views

How close is a typical New Moon to the Sun in the sky?

In a Solar Eclipse, the Sun, Earth and Moon are exactly colinear (well some area of the Earth where the eclipse is visible), and these are relatively rare. But in addition, Sun, Earth and Moon are ...
Bennet's user avatar
  • 213
1 vote
1 answer
199 views

What phases of a moon orbiting Proxima Centauri b could be seen?

Assuming a moon like Earth's natural satellite would be orbiting the Proxima Centauri b at a similar distance, what moon phases could be seen from the planet's surface at coordinates 0;55? Adding ...
Krišjānis Liepiņš's user avatar
11 votes
3 answers
2k views

The shape of the moon limb/crescent (terminator line)

Given that that n% of the moon is illuminated. I want to (approximately, but more or less correctly) draw the the terminator line on the circle (that represents the ...
WHITECOLOR's user avatar
7 votes
1 answer
765 views

Calculate moon illumination given moon age

trying to compute moon illumination percent from moon day. To get moon day in pseudo code I do: ...
akostadinov's user avatar
1 vote
1 answer
94 views

How long before two sidereal months start on the same lunar phase?

I was reading about the difference between the sidereal and synodic month when I started to wonder how many sidereal months need to pass before you get two that start on the same part of the synodic ...
Washtun's user avatar
  • 13
3 votes
1 answer
104 views

Metonic cycle observation & display [closed]

I'm unable to locate physical display observatories for the 19 year Metonic cycle. How do I display this information & calendar detail on a concrete floor near the tropic of cancer? I seek a floor ...
Eric Snow's user avatar
2 votes
2 answers
2k views

What kind of effects would two moons have on an earthlike planet?

On Earth our moon has several effects: it generates two high and two low tides a day; it slows down the spin of the planet and stabilizes its wobble, etc. So, what possible effects could two moons, ...
CuriousExplorer's user avatar
3 votes
1 answer
148 views

New moon rise same spot on horizon as sunrise, almost same time [closed]

I witnessed the new moon rise just ahead of a sunrise at the very same spot on the horizon. How often could I plan on looking for that occurrence again?
Ruby Moseley's user avatar
8 votes
2 answers
574 views

Trying to understand lunar phases

Complete novice here. I'm trying to understand what appears to be two approaches to quantifying lunar phases. Have I got this right? Named lunar phases can be understood as the Moon's ecliptic ...
Peter's user avatar
  • 1,033
1 vote
0 answers
343 views

JPL Ephemeris or Skyfield - how to get moon phase percentage (not illumination percentage)

I know how to use JPL's Horizons to get moon illumination percentage but I noticed that even at new moon, the illumination never goes to zero: ...
Bob's user avatar
  • 213
3 votes
2 answers
387 views

Why doesn't lunar perigee always occur in the same lunar phase?

If the phases of the moon and the moon's perigee are just dependent on the point that the moon is in through it's orbit, why can perigee happen at different phases of the moon? My thinking is this: ...
Krill_Bill's user avatar
2 votes
0 answers
547 views

tool to calculate moonrise/moonset and moon phase for any date for any location

I have googled for such a solution but I have not found anything substantial: I found one website but it was someone's side hobby so my confidence in it is low. Thankfully, I have discovered ...
Bob's user avatar
  • 213
7 votes
3 answers
2k views

How often does a full moon happen on the weekend?

Wikipedia says that a synodic month has a length 29 d 12 h 44 min and 2.9 s. I'm interested to find out how often a full moon (but actually, it's the same for any phase) happens during a weekend. I ...
Mark's user avatar
  • 359
5 votes
1 answer
335 views

Is there a word or short phrase that denotes the apparently moving part of the lunar limb?

Between new moon and full moon, the moon's disc as viewed from the earth is bounded by a semicircular arc on its right and an arc on its left that moves to the right until at full moon it forms the ...
user avatar
7 votes
2 answers
2k views

what percent of moon must be illuminated to be visible with naked eye and clear sky?

Originally, the new Jewish month was determined by the sighting of the new crescent moon. There are online calendars that give percentage of moon that is illuminated. Using the computations from these ...
Bob's user avatar
  • 213
15 votes
6 answers
9k views

How is this picture of the moon possible?

I need help understanding this images I personally took. If the phases of the moon are determined by the position of the earth, moon & sun. Then how is the moon a crescent while it is rising in ...
Cody Page's user avatar
  • 151
0 votes
0 answers
181 views

looking for a plugin or API for Moon-phases and sky-map

I want to create a website that contains star maps and moon phases like mapiful and thatverynight but couldn't find any helpful APIs or plugins. Can anyone help? thanks
JSK's user avatar
  • 1
3 votes
2 answers
179 views

When can Moon occult Venus?

I'm trying to solve this task: At what age of the Moon (in days after the new moon) is it possible for the Moon to occult Venus? How I was solving it: Angular velocity of the Moon is 13.2 degrees ...
ALiCe P.'s user avatar
  • 1,017
3 votes
1 answer
3k views

What percentage of the time can we see the moon during the day?

From sun rise to sun set what percentage of the time is the moon visible? I saw one thing at the top of google saying an average of 6 hours a day but that seems like a weird way to answer it. Would ...
Beans's user avatar
  • 551
3 votes
0 answers
68 views

Is there software that will let me calculate things like lunar phases and the position of bodies in the sky in a custom solar system?

I am constructing a fictional solar system and want to be able to calculate astronomical events and locations, like lunar phases and eclipses, plus the positions of other astronomical bodies in the ...
Lawton's user avatar
  • 131
1 vote
0 answers
38 views

How to determine how often a planet's center will be collinear with its moon's?

Expanding on the question: Let's say I have a planet orbiting some star (earth-like, sun-like, for the sake of example). If this planet has two moons, M1 with orbital period of 30 earth-days and M2 ...
PedroGaya's user avatar
6 votes
1 answer
603 views

Would people on opposite sides of the earth see different details of the moon, if so are there actual photos demonstrating this?

I am aware of phases and the fact that opposite sides will see the moon flipped relative to the other but what I’m asking specifically is would the almost 8000 mile difference between the two ...
Beans's user avatar
  • 551
1 vote
1 answer
139 views

What are the aspects does the moon differs between cities located on the same latitude?

What are the aspects does the moon (astronomical position and other astronomical aspects) differs between cities located in the same latitude? - For example: Seattle, Munich, Vienna, and Ulaanbaator ...
huab's user avatar
  • 143
0 votes
1 answer
333 views

Apparent Magnitude of First quarter Moon [closed]

Given Apparent magnitude of moon is -12.5. Distance of moon and earth is 384400 km. Diameter of Moon is 31 arcmin. Phase of moon is 0.5. Find the apparent magnitude of first quarter moon.
Rutherford paul's user avatar
10 votes
2 answers
2k views

Is there a precise definition of "Supermoon"?

Elsewhere online I keep reading that a supermoon is the situation when full moon coincides with moon perigee. But see this plot from wikipedia Lunar Distance entry The perigee distance varies wildly ...
arivero's user avatar
  • 153
1 vote
0 answers
293 views

How to get the percentage of the Moon illuminated as a function of time?

As the title suggests, I need a way to get the percentage of the Moon's disk which is illuminated as a function of time. There are simple geometrical expressions for the fraction of a sphere ...
Arfmann's user avatar
  • 119
1 vote
0 answers
87 views

Moon cycles used for gardening & harvesting

I appreciate that this question may deviate from the standard astronomy questions. I have recently read an article that suggest that gardeners, farmers & winemakers etc sometime use the moon's ...
Will's user avatar
  • 11
1 vote
1 answer
66 views

Is it easier to see the young moon when it's closer to the sun?

With the naked eye, would it be easier to see the moon when it's close to the sun, because it might reflect some more light (or not, I'm not sure) or farther from the sun because the sun shines ...
mesrefoglu's user avatar
16 votes
5 answers
31k views

Why can I see sometimes a horizontal half moon instead of a vertical one?

Why do I sometimes see a horizontal half moon, instead of the more usual vertical one? I keep getting answers for crescent moons, but this is a half moon with its curve closer to the horizon, like a ...
Evilin Garnett's user avatar
6 votes
1 answer
879 views

Moon phase angle

When I look at a visible moon in daylight its phase is shown at an angle. However textbook moon phase diagrams only show the phase vertically. What is it that determines the angle? The reason I ask ...
Jen's user avatar
  • 61
3 votes
1 answer
622 views

Determining the percentage area of the moon's disk shaded with respect to time

I've looked online and I've found sources such as this paper on a lunar phase simulator as well as this article about lunar phases. I'd like to be able to model the area of the lunar disk which is ...
akshat's user avatar
  • 131
3 votes
2 answers
610 views

How to map moon phase number + "lunation" to moon phase name?

I am querying an API (weatherbit) which returns a moon phase number which looks like this: 0.9594168 For the 16 days I look at the numbers vary from 0.006 to 0.99. I have 8 "moon phase" ...
Michael Durrant's user avatar
3 votes
2 answers
225 views

What are "p" and "r" wrt the moon?

Still learning, thinking - and failing - about the moon. timeanddate.com has this cute and dynamic moon sketch at e.g. https://www.timeanddate.com/moon/uk/london They generate this based on three ...
Marcel Stör's user avatar
0 votes
2 answers
304 views

Mapping illumination to moon phase (font) icon

I use algorithms that give me the moon phase, age and illumination (and more) for a given timestamp and location. I am struggling to map that information to a (font) icon of the Moon Phases font. Each ...
Marcel Stör's user avatar
0 votes
1 answer
113 views

Historical Lunar Tables and the Associated Error Bound

Consider as an example, AstroPixel's ``Six Millennium Catalog of Phases of the Moon''--- http://astropixels.com/ephemeris/phasescat/phasescat.html My question is two-fold: How are these tables which ...
DDS's user avatar
  • 137
1 vote
0 answers
57 views

Ladakh India where the moon (Ramadan moon) is sighted but not in rest of India [duplicate]

Today 22 May 2020 around 3 p.m Ladakh India sighted new moon(Ramadan moon) but not in rest of India.I read many articles acc. To them it is not visible today, then how it was seen from Ladakh... .
nasir mehdi's user avatar
-3 votes
1 answer
155 views

Where is the Moon?

I live in Western Australia and I have not seen the moon for almost a solid week. Last I saw it it was almost full, and the sky has been clearer than ever with all the stars bright and visible yet the ...
Aisha Hoft Withers's user avatar
3 votes
1 answer
10k views

How to calculate moon overhead and underfoot time?

For hunting purposes, some hunters follow the moon phases to hunt accordingly. To give some context, here's some links: Lunar cycle's effects on hunting: https://www.acurite.com/blog/weather-stations-...
Amine Z.'s user avatar
2 votes
2 answers
2k views

Is it possible to explain the difference between synodic month and sidereal month by degrees?

Is it possible to explain the difference between synodic and sidereal month by degrees - in the following way? Just recently I learnt about these two types of months, and I want to see if I can ...
Reckless Glacier's user avatar
1 vote
1 answer
325 views

Simple question about the phases of the Moon

If on March 20 the Moon were located at the position of the sun, how can I determine the phase in September 22, June 22, and December 20? I drew the orbit and calculated by dividing sidereal days to ...
scitamehtam's user avatar