Astronomy Stack Exchange
Astronomy Stack Exchange

Questions tagged [moon-phases]

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

102 questions
11
votes
3 answers

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 moon). Orientation is not the case here, just the crescent shape. What is the…
WHITECOLOR
  • 213
  • 1
  • 7
7
votes
1 answer

Calculate moon illumination given moon age

trying to compute moon illumination percent from moon day. To get moon day in pseudo code I do: LUNAR_MONTH = 29.530588853 KNOWN_NEW_MOON = JulianDay("2000-01-06 06:14") age = (julian_day_now - KNOWN_NEW_MOON).abs % LUNAR_MONTH So that shows me…
akostadinov
  • 235
  • 1
  • 4
7
votes
3 answers

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 thought: a weekend lasts 48 h a week has 168 h a…
Mark
  • 359
  • 1
  • 7
7
votes
2 answers

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 calendars, what is the minimum illumination…
Bob
  • 213
  • 1
  • 5
6
votes
1 answer

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 this questions is the Moon's illumination is not in…
Jen
  • 61
  • 2
5
votes
3 answers

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 === Actually, I'm preparing a calendar of lunar phase…
DevonDahon
  • 163
  • 7
5
votes
3 answers

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 newbie, less than a layman, to astronomy - but I am…
Luis Masuelli
  • 151
  • 1
  • 3
4
votes
3 answers

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 the evening, but later on, as the moon is setting,…
Melvin Hurst
  • 41
  • 2
3
votes
3 answers

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.
aquaelmo
  • 33
  • 1
  • 1
  • 3
2
votes
1 answer

Is this a wet moon?

Tonight around 12:20 AM I realized that the top part (instead of the side) of the moon was missing. I live at a country in the tropics. I took this picture with my phone so it isn't very good. After googling I found out about the wet moon phase in…
artificer
  • 123
  • 2
1
vote
1 answer

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://svs.gsfc.nasa.gov/5187/ is: Celestial north is up…
Reginald
  • 11
  • 3
1
vote
0 answers

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 the distance to its moon), it is waxing. This is because at…
AlgebraicsAnonymous
  • 191
  • 9
1
vote
0 answers

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 illuminated by a collimated coplanar light source, but I…
Arfmann
  • 119
  • 1
0
votes
1 answer

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 the code. I already have the (java) code for…
ccpizza
  • 103
  • 5
0
votes
1 answer

A moonless night

How can I tell in each month, when here will be no moon shining or seen at night?
Norm
  • 11
  • 1
1
2