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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23 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 ...
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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 ...
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58 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 ...
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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.
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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 ...
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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 ...
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52 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 ...
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1answer
38 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 ...
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1answer
90 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 ...
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1answer
83 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 ...
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2answers
344 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" ...
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1answer
61 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 ...
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78 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 ...
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1answer
56 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 ...
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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... .
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103 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 ...
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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-...
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2answers
672 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 ...
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1answer
62 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 ...
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Calculating the position angle of the moon (the rolling back and forth)

I have been watching the the NASA Moon Phases Video of the year 2020. Pretty much everything makes sense and I know how to calculate it including the moon phases, declination, azimuth, apogee and ...
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How do I calculate moon phase orientation at any Coordinates given all the necessary data?

I'm having a problem for a couple of days where I'm trying to accurately calculate the phase angle of the moon at any given Coordinates (lon,lat).If I know my current Coordinates, Moon and sun ...
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1answer
284 views

Jean Meeus - calculating moon rise, transit and set times - help isolating error in logic

I've been working my way through the Jean Meeus Astronomical Algorithms book for a few weeks, to implement some of the key algorithms for a personal project. This task has been a little more complex ...
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1answer
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How to calculate the moon phase angle?

I need to calculate the exact moon phase angle for each our of a day. I have my position in lat and long and a unix timestamp. At the end i would like to be able to caluculate the moon brightness with ...
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1answer
130 views

How many Moon's Topocentric Conjunction occurs per lunar month?

It is clear that only one Moon's Geocentric Conjunction occurs per lunar month, what about the Topocentric Conjunction for a given location? without scale I can imagine many Topocentric Conjunctions ...
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3answers
652 views

Get a table of Moon phase angle per day

Where can I get a table with the Moon phase angle for each day ? It's available here for a given day, but I would have to input each day of a year to get a full table. === NEW EDIT : 2019-09-18 ===...
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1answer
157 views

Did NASA/JPL get “waning” and “waxing” backwards in this video?

The NASA JPL video What's Up: September 2019 Skywatching Tips from NASA says (per both the closed captions and audio): We’re in a several-month period right now when the new Moon falls right around ...
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1answer
77 views

Relation between phase and magnitude

Given the phase of a planet or satellite, I can find the area illuminated visible to us, if we consider a 2D surface. But how do I find the percentage of illuminated area visible considering it a 3D ...
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3answers
858 views

Struggling to understand the phases of the moon

Source Typically this diagram is how the phases of the moon are explained but the issue is this, namely, the phases seen on the right half are not possible. All the phases should appear on the left ...
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evaluate solar eclipse Besselian elements? [closed]

I found this NASA website which says that to predict eclipse, we should solve the Besselian elements ..what does this mean, how can I solve for Besselian elements? Is there a numerical method? I need ...
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Is it possible to do moon sighting in advance for 5 years with 100% accuracy? [duplicate]

It is Ramzan and the usual heated disagreements between clerics here in Pakistan as to the sighting of the crescent. This time the minister of Science and Technology (who is not a scientist himself ...
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1answer
79 views

Moon's path as seen from Earth

As observed from the surface of Earth: Will the moon ever repeat the same path (trajectory)? If yes, what is the period of repetition? And also will the moon cover the night sky with its path ...
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1answer
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How to calculate the time of Ekadashi days?

Is there an official reference algorithm for calculating the Ekadashi days? I found the textual description of Ekadashi calculation on wikipedia but can't really make sense of it in order to write ...
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1answer
301 views

What causes the duration of moon phases (the time the moon is visible above the horizon) to vary for an observer in the northern hemisphere?

Why does each phase of the moon stay up a different number of hours per phase, so that, for example, January’s full moon was up twice as long as the new moon? Plus every month this bulge shifts and at ...
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2answers
461 views

Lunar phases if Earth was tidally locked to the Moon

I know that the Earth will never become tidally locked to the Moon, so this is purely hypothetical. If I understand correctly, in this hypothetical scenario an Earth day is now a lot longer at ...
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1answer
83 views

Lunar illumination (percentage) data on an eclipse day needed

I am looking for the information on the percentage illumination of the moon during the different stages of a total lunar eclipse. Is there a database from where I can acquire information of lunar ...
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1answer
725 views

What is the Terra phase?

Does the Moon have a night and day like Earth? When sitting on the Moon and viewing the Earth what does it look like when the Earth goes through phases like the Lunar Phase? How does the sun travel ...
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Why moon sighted only in Kerala but not in rest of India?

I know for most of you the question may look silly, but Kerala is a state in India where the moon (Ramadan moon) will be sighted but not in rest of India. I was reading the news article where I got a ...
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1answer
44 views

Ancient greeks know about leap day? [closed]

I'm reading about Antikythera machine and its functions. So I read about solar cycle and moon cycle and how they used 19 solar years to compare with 235 lunar cycles. So this is my question: They ...
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1answer
390 views

A moonless night

How can I tell in each month, when here will be no moon shining or seen at night?
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How do I calculate the hour angle of a planet's moon from a point on that planet's surface?

I'm worldbuilding and I'm trying to construct a standing stone calendar that'll accurately denote where to look for my planet's moon at its four major phases from 53.8 degrees South. So, I need the h0,...
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1answer
16k views

How does the Moon look like from different latitudes of the Earth?

I have heard, that on the northern hemisphere, you can estimate a direction of south if you imagine a line going through the tips of the border between illuminated and shadowed part of the Moon, and ...
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1answer
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Does a set moon sky equal a new moon sky?

I am planning some astrophotography. And comparing two times. On one night I plan a midnight shoot when a waning crescent moon rises at 1am. This is 1 week ahead of the new moon. The other night ...
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2answers
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What does the information about the current Moon phase help me as a layperson?

I have just watched an interesting video about Moonphase watch. But why would I need to know about current Moon phase anyway as a layperson? I just can't think of any practical application for the ...
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2answers
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Why the moon is blinding me right now?

I'm on the most northern part of Germany (Schleswig-Holstein) it is 11.20pm right now and the moon is here as bright as I never saw it before I was just outside and it is as bright as if it was dim ...
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What would be the required conditions for a lunar eclipse to occur only once on a precise annual basis?

As I am aware, lunar eclipses can take place several times a year on Earth. However, I am curious whether it would be possible for this event to only occur once annually on a specific date (and ...
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786 views

Why did the moon have a distinct reddish edge tonight?

In Monterey, California, with a "half-moon" high in the sky at about 9 pm (2017-08-30), the moon had a distinct red outline on the outer edge of the NE quadrant; for awhile I saw it also on ...
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Does Earth illuminate the unlit part of the Moon as [duplicate]

... today is August the 17th? I just saw the moon (4:30 CEST) and I have the strong impression that the unlit (by the Sun) part of the Moon is anyway "visible" as a very very dark grey portion. It ...
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1answer
822 views

calculating lunar phases

Given a date, I'd like to return the lunar phase. Jean Meeus's Astronomical Algorithms book and the many packages like PyEphem that make use its algorithms provide ways to calculate when a primary ...
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1answer
249 views

If I had a horseshoe orbit of two moons…

Consider an Earth-like planet, with two moons. I guess the two moons would have to be smaller than our own, for the system to be stable. Is that stable? I did some research, and apparently Janus and ...
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1answer
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Does the new moon appear at the same time around the world or in one region last [duplicate]

My query is basically, say for example if the new moon is seen in the Middle east region, does it mean that it was the day of new moon in sub continental country as well ? You can't have a new moon in ...