Questions tagged [sunrise]

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2 votes
2 answers
69 views

How to find the first Julian day with the same Earth-Sun constellation

There are quite some sources for astronomical calculation formulas, e.g. Astronomy Answers: Position of the Sun, which is e.g. used by KDE's Night Color plugin to calculate the time of a sunset or ...
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1 vote
1 answer
73 views

What is the "sunrise equation" for non-constant declination component?

The standard Sunrise Equation (refraction neglected) is this: $$ \cos(\text{hour angle}) = \tan(\text{declination})\tan(\text{latitude}) $$ This equation - which really has nothing to do with the Sun ...
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1 vote
2 answers
149 views

Why do sunrise/sunset times (for a given location) vary based on the source of the data?

I've noticed that different reputable weather websites will give different times for sunrise/sunset for the exact same location. I've seen variation by 25 minutes or more, for sunset on the same date ...
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4 votes
2 answers
878 views

Why isn't Spring equinox on 1st of April?

AFAIK the summer and and winter solstices are based on longest day and longest night doesn't fall on 1st of Jan and July 1st because we consider the day to begin and end when the middle of the sun is ...
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3 votes
1 answer
86 views

How can I calculate my position (lat/lon) given a sequence of solar-elevation measurements at known times?

The "forward" problem (given time and lat/lon, find solar position angles) is well documented, e.g. here. I am trying to figure out the "inverse" problem: given time and [a ...
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2 votes
0 answers
52 views

Daytime length and sunrise / set cardinal directions

Let me illustrate the question with an example. On Feb 2nd 2022, the sun rises in Los Angeles at cardinal direction 110 and sets in direction 250 (according to timedate website). This means that the ...
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  • 21
2 votes
0 answers
49 views

How long is the sunrise (or sunset) on North (or South) Pole? [duplicate]

I wonder how to calculate the duration of the Sun crossing the line of the horizon on equinox on Pole. For equator I used this formula: $t = \frac{2 \times p}{\cos(\phi) \times u}$, where $u$ - is ...
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  • 1,017
4 votes
1 answer
82 views

Difference in Sunrise times between Horizons and NOAA

I used the NOAA solar calculator at https://gml.noaa.gov/grad/solcalc/ to generate the sunrise time for today. ...
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6 votes
1 answer
243 views

Can stars really be seen after sunrise from Mount Everest?

I came across this image taken on the "Balcony" at over 27,000 ft (8,200 m) elevation, beneath the summit of Mount Everest. So many stars can be seen on it even though the Sun has risen. Do ...
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0 votes
2 answers
81 views

Given a location and a time on another planet, how do you determine how many hours before or after sunrise is it there?

I'm actually not so much interested in sunrise/sunset times. What I want to know is how to relate local planetary coordinates (e.g., planetary lat/lon) to, for example, heliocentric coordinates at a ...
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1 vote
1 answer
51 views

Tracking the Sun from Sunrise in the East to Sunset in the West

Is there a Correct way to mathematically allocate GPS/location of Azimuth Degrees ? EG: In the Southern Hemisphere, if North is 0 degrees, for say Sydney is direct East 90 or -90 degrees ? Then what ...
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4 votes
1 answer
808 views

Straightforward derivation of the sunrise equation

I'm looking for a reasonably straightforward derivation of the sunrise equation$$\cos\omega=-\tan\phi\tan\delta$$as referenced in the Wikipedia article here. I've dipped into Astronomical Algorithms ...
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  • 559
0 votes
0 answers
33 views

What is the formula to input date, time and longitude. Where I can get latitude of the civil twilight back?

I am making a watch app, where I need to know where there is currently sun, and where it's not. I need to have some sort of formula/function to insert: date, time and longitude, and get back the ...
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  • 101
2 votes
2 answers
210 views

Angle the Sun makes with the horizon during sunset

Let's say it is the day of the summer solstice and the Sun is setting at 23.5 degrees declination. I am at let's say, 10 degrees latitude. How would I go about calculating the angle of the Sun below ...
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3 votes
1 answer
98 views

Is it safe to look at an annular eclipse during sunrise? [duplicate]

I'm lucky enough to be where an annular eclipse will happen at the same time as sunrise. Usually, it's dangerous to look at an eclipse directly. However, the sun appears much less bright at sunrise. ...
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0 votes
1 answer
66 views

Is the appearance of the twilight not constant in the interval before the sunrise?

I've been told by an astronomer in past, that the appearance of the twilight isn't constant in the interval before the sunrise. That is to say that not every day the earth is going at the same speed, ...
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2 votes
1 answer
197 views

How does one use SPICE to calculate sunrise and sunset?

I've seen it mentioned here that SPICE can be used to calculate sunrise and sunset. How? According to the official documentation, SPICE is used to calculate: Time system conversions Positions of ...
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2 votes
1 answer
174 views

Does the Time of Sunset (Sunrise) Change Over Time Given a Fixed Location and Consistent Atmospheric Conditions?

Assumming a fixed location, clear skies, and consistent atmospheric conditions, does the sunset (sunrise) time change over time? For example, sunset on February 3, 2021 in Tel-Aviv, Israel, is ...
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3 votes
1 answer
27 views

Timing based on upper or lower part of sun/moon

When you time an astronomical event, such as the moon/sun rising above the horizon, do you note the time when the the first sliver breeches the horizon or when the bottom of the moon/sun just becomes ...
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  • 1,519
15 votes
5 answers
8k views

Does the sun's rising/setting angle change every few months?

When I lived in Darwin, Australia, I noticed that the Sun set in a slightly different direction to the West. In the evenings, I used to sit on a couch and watch TV. There was a huge window to my right ...
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2 votes
1 answer
287 views

Why both sunrise and sunset use the position of the sun's upper limb?

It is my understanding, that astronomical moments of both rise and set use the relative position of background object's upper limb to the foreground object's horizon. When were these definitions ...
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1 vote
1 answer
88 views

Why the earth orbits the sun from X to -X and not the opposite [closed]

I wonder all the time, why the earth orbits the sun as expected from east to west(X to -X) ? It could be different, for example from the west towards the east . What would happen if that were the case?...
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7 votes
1 answer
846 views

problems finding rise set and transit times at high latitudes using Meeus' algorithms

I am implementing Jean Meeus' algorithm from his book "Astronomical Algorithms", 2nd ed. for rise, set and transit times in Swift. It seems to provide very good results (no more than 1 ...
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  • 181
1 vote
1 answer
276 views

How to calculate sunrise and sunset on on a given date and location?

I have a given date at any time in future or past eg: 2016-04-23 or 2022-05-12 Now given at any location(lat,lng). How do i find the time of sunrise or sunset.
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3 votes
2 answers
320 views

Is the equinox absolutely true east everywhere?

I've read that only only in the equinoxes do you get to see the sun rise in the exact east regardless where you might happen to be. However I think this is not absolutely true everywhere, but only in ...
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5 votes
1 answer
332 views

Was the Earth-Sun distance ever calculated based on the time difference between night and day?

If we define sunrise and sunset as the time when the center of the Sun goes over the horizon then day time is a little bit shorter than night time because from a single point one cannot see a complete ...
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3 votes
0 answers
50 views

Would Martian sunrise/sunset look the same at the Thaumasia Plateau as the rovers' photographs?

If observing the sunrise or sunset, with the naked eye, from the Thaumasia Plateau (app. 260°, -10°), 6 kilometers above Mars elevation zero, would it have the same blue hue as the images of the ...
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  • 1,449
3 votes
1 answer
86 views

How long for the sun to traverse its diameter at the pole?

As the sun rises once per year at the north/south pole, the time taken to rise (and set) must also take significantly more time to complete to rise (and set). How long does this take at either pole? ...
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  • 31
4 votes
2 answers
217 views

Sunrise and sunset times when compared between the vernal and autumnal equinoxes

Why is it that sunrise and sunset occur at different times when compared between the vernal and autumnal equinoxes? Consider Pontianak, Indonesia, 0 deg N, for simplicity. Timeanddate.com gives ...
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2 votes
1 answer
166 views

Solar azimuth for celtic fire festivals

I am pretty new to astronomy, and I have fallen down rabbit hole creating a new Metonic calendar in Javascript. As part of this I would like to calculate when the sun is half way between a solstice ...
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5 votes
1 answer
113 views

Daylight Time Expansion

I live in northern hemisphere around 44th latitude. Starting from Winter Solstice, December 21, 2018 the duration of daylight is naturally increasing. What I observe, however, is that the duration ...
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0 votes
1 answer
252 views

Sunrise - from earth - sun position or when sun rays reaches earth?

Time for the sun rays to reach earth is approximately 8 mins. If time of the sun rise is 7:30 - which time is this? Time when sun rays reaches earth or time when earth and sun comes into correct ...
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  • 103
1 vote
0 answers
45 views

What's the time in which the sun rises? [duplicate]

What's the time the sun takes in order to rise? (The time in which the solar disk crosses the horizon) How does this time depend on local latitude and the sun's declination? Assume that we're at sea ...
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3 votes
1 answer
150 views

Predicting accurate time of local sunrise in mountainous area?

Is there any software which will tell me accurately at what moment any part of the solar disk will become from a specific point on the ground taking account of terrain. I feel like Google maps should ...
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  • 9,893
5 votes
1 answer
3k views

Does the sky get darker faster during the winter?

When one lives away from the equator, say at around 37° latitude, does the sky get darker faster after the sun sets in the winter as compared to the summer? Why is this the case? I believe that if ...
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