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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43 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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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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949 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-...
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355 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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50 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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169 views

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
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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
452 views

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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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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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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152 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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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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395 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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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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578 views

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
164 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
312 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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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
693 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
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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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333 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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175 views

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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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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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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Why do I need to know about moonphase?

I just watch an interesting video about Moonphase watch. mmm... but why do I need to know about moonphase anyway, I just can't think of any practice for the moonphase indicator on the watch?
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492 views

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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1answer
964 views

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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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 the outer ...
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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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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
238 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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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 ...
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3answers
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What should I consider in order to accurately calculate the moon phase?

Although this question apparently addresses the topic, it does not tell appropriate factors involving the moon phase. I found two distinct algorithms. this one and also this one. I am less than a ...
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4answers
10k views

Is the full moon full everywhere on the planet?

When the moon is full, fully lit by the sun, will it appear full everywhere on the planet? E.g. if I where to set the date for the next three full moons for say: Sweden, Bali and Seattle how ...
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Why can I see the dark side of the moon?

Last weekend (29/30 April) the sky in my area (Central Europe) was pretty clear and the Moon was nicely visible. Funnily, one could not only see the sunlit area of the Moon, but also the dark side* ...
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Changing Appearance of the Moon During a Single Night

I have noticed that the inclination of the moon at a given location varies throughout the night. From the UK, the terminator in a half-moon is clearly sloping from top left to bottom right early in ...
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How does the length of the minor semi-axis of the moon's disc's inner terminator vary through the cycle?

The curve that separates the bright and dark parts of the moon's disc as viewed from the earth is called the inner lunar terminator, which is semi-elliptical in shape. We can model the disc as a unit ...
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1answer
499 views

How can I calculate when the new moon will be observed from a particular meridian?

I have read that Chinese months start on the day on which the new moon is observed from the 120th meridian east. From this I am assuming that the new moon is observable from there each time and that ...
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385 views

How often is a blue moon?

A blue moon is two full moons in the same month. How many times will a blue moon occur in the average lifetime of say 70 years?
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lunar calendar accuracy for predicting new moons

I wonder, how accurate the lunar calendar is? Can we predict the new moons precisely for tens of years in future? If we know all factors that affects the movement of the moon, then why it is not ...
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56 views

What is the name of the cycle whereby the lunar azimuth and altitude recur on a given day?

Like the Metonic cycle, except for position in the sky, not phase. Original question: If I look up at the moon tonight, how long before it is in the same apparent position, and same phase, again? I ...
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1k views

How Soon Could a Waxing Crescent Moon Be Seen?

Question: Apart from a Solar Eclipse, How much time is needed until a Waxing Crescent Moon be seen following a New Moon? Would the time of year be significant? The Vernal Equinox + 1 Month. Could it ...
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210 views

Moon SHAPE calculator

I have seen a lot of information about moon phase calculation, but need an accurate moon shape calculator/algorithm given the observer's position and time. This implies that the illuminated portion ...
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124 views

How to figure out a moon phase for July 1937

I would like to know how to figure out the moon's phase for July 4, 1937 at 9:34 pm. Thank you.
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How to calculate when the moon is highest in the sky to the earthbound observer?

Like when is the new moon highest in the sky? Or third quarter? How do I know this for any general moon phase? Thanks.