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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1answer
37 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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4answers
11k 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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1answer
82 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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2answers
594 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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0answers
39 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... .
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1answer
53 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
7k views

Why can I see the whole moon during various non-full-moon phases?

Here's an image that describes the phenomenon I'm asking about. The very thin sliver to the left is of course the surface of the moon as lighted by the sun. But the rest of the moon is also faintly ...
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3answers
548 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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2answers
324 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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2answers
2k views

Formulas to determine the illuminated phase and orientation of the Moon

The phase of the Moon (the bright limb) looks different depending on where on Earth the observer is located and the time of the observation. I've located this video and the accompanying spreadsheet ...
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1answer
67 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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2answers
64 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
53 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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1answer
2k views

Is there a simple, analytical formula for the lunar phase brightness curve?

Brightness of the lunar disk varies as a function of phase angle. This phenomenon is very well established, as is the increase in brightness at low phase angles. Is there a simple analytical formula ...
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1answer
14k 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
54 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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3answers
4k views

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.
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1answer
908 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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1answer
101 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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1answer
2k 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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1answer
57 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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0answers
336 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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0answers
307 views

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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3answers
621 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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1answer
239 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
118 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
8k views

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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1answer
155 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
784 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
75 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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0answers
298 views

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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2answers
2k views

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
540 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 the outer ...
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1answer
76 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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3answers
2k views

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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1answer
928 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
217 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
415 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
719 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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3answers
6k views

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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1answer
9k views

From which country or area is the new moon visible first?

Being able to see the Moon is dependant on various factors like sunset timing etc. Considering all these factors, which country or area of the world sees the new moon first? I am asking about the new ...
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2answers
1k views

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
366 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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0answers
183 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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1answer
38 views

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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0answers
72 views

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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2answers
593 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
1k 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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0answers
61 views

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 ...