# Tag Info

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

The Sun rises and sets at a different point on the horizon every day. The change is small, so without careful observations, it may take several days or weeks to be fully aware of the change. ...
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### Does the sun's rising/setting angle change every few months?

You're not silly1, it certainly swings back and forth (North and South) one full cycle every year. It's directly related to why days are longer in the summer and shorter in the winter. I am no expert, ...
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### How can the new moon set before the sun, as will happen in some locales on November 13, 2023?

This is because the New Moon is defined as the moment that the moon is at the same ecliptic longitude as the sun. It may be several degrees above or below. The situation for moonset on Nov 23 is shown ...
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### How long do the phases of sunset take?

@Calc-You-Later's answer is correct in places where the path of the Sun is perpendicular to the horizon (at the equator during the equinoxes, somewhere between the tropics the rest of the time). There,...
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### Why isn't Spring equinox on 1st of April?

The calendar is designed so the 21st of March is set to the spring Equinox, and everything else is calculated from there. So the reason that the equinox doesn't occur on the first of April is boring. ...
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### Straightforward derivation of the sunrise equation

We can start by converting between equatorial coordinates (right ascension $\alpha$ and declination $\delta$) to horizontal coordinates (azimuth $\text{Az}$ and elevation/altitude $a$). If you want to ...
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### Does the sun's rising/setting angle change every few months?

This answer is a supplement to the existing answers. I looked around for nice graphs showing the sunrise azimuth over the year for various latitudes, but I couldn't find anything suitable. So I just ...
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The Sun's apparent angular diameter is approximately 0.5 degrees - though atmospheric conditions can make this vary. We can calculate how fast the Earth rotates in degrees per minute like so: $24h\: ... • 1,443 7 votes Accepted ### Was the Earth-Sun distance ever calculated based on the time difference between night and day? You have a good idea. You mentioned 4 effects already (clock accuracy, latitude, time of year, and clear horizon), but there is another effect that is larger than those: atmospheric refraction. ... • 8,032 7 votes ### Does the sun's rising/setting angle change every few months? The Sun does indeed drift across the sky throughout the year, not only rising higher in the summer and lower in the winter, but also varying along an east-west axis. This can be shown by observing the ... • 2,274 6 votes Accepted ### Geometric effect on sun's position in the sky at the equator At the equator, there is no geometric effect at all—the Sun's daily track above the horizon is always exactly half a circle. The issue is the definition of "half a circle". What this refers ... • 8,032 5 votes ### How long do the phases of sunset take? For a quick and dirty approximation, let's assume a constant Sun angular diameter of 32' and no atmospheric refraction. Let$\varphi$be the observer's geographic latitude, and$\delta$be the Sun's ... • 18.7k 5 votes ### Angle the Sun makes with the horizon during sunset Short answers: It's not just angular velocity of Earth's rotation times elapsed time. You do need to factor in declination and latitude. Using your representative date and observer location: The ... • 1,791 5 votes ### Angle the Sun makes with the horizon during sunset The transformation from the equatorial coordinates to altitude (azimuth is not important) is given by $$\sin{a}=\cos{h}\cos{\delta}\cos{\phi}+\sin{\delta}\sin{\phi}$$ Let's say that$t=0\rm\, s$at ... • 2,879 4 votes ### what degree in the sky does the sun change color? Here's a partial answer: As mentioned in the comments, the transmission of the atmosphere depends quite a lot on local factors. But given a transmission$T_0(\lambda)$at zenith, the transmission at ... • 38.6k 4 votes ### How to find the first Julian day with the same Earth-Sun constellation Most formulas accept a Julian Day as input, but internally usually use the number of days (or years, or centuries) since Jan 1, 2000 12:00pm. Take the function below, which accepts JD as input, but ... • 5,922 4 votes Accepted ### Where can I download the historic sunrise and sunset times for a location? You might want to find an astronomical almanach or year book. They usually have tables of sunrise and sunset times. They usually cover only one year, though and accurate times only for selected places.... • 19.8k 4 votes Accepted ### Sidereal time of rising and setting of the sun on the arctic circle You need to intepret the question a bit. By "June 22" they probably mean "Summer Solstice", likewise for "Dec 22". At the solstice the right ascension of the sun is 6hr/... • 123k 4 votes Accepted ### What is the distance between sunrise and sunset along a parallel of latitude for declination other than 0? We can use the sunrise equation to determine the Sun's hour angle at sunrise & sunset and thence determine the daylight length. The sunrise equation is derived from the solution to the PZX ... • 14.9k 3 votes Accepted ### Does the Time of Sunset (Sunrise) Change Over Time Given a Fixed Location and Consistent Atmospheric Conditions? Shalom! Strictly speaking, yes, the time of sunset does change, but the amount of change is imperceptible to humans over a lifetime. The change is due to the slowly varying obliquity of the Earth on ... • 7,502 3 votes ### Does the sun's rising/setting angle change every few months? I hope someone can come along and make this more precise, but I'm pretty sure the effect is greater the further you move away from the equator. So it would be more noticeable in Canberra (35° S) than ... • 131 3 votes ### How to find how many degrees from the beginning to the end of the sunset? The mean angular radius of the Sun in radians is $$\frac{R_\odot}{\mathrm{au}} = \frac{6.96 \times 10^5~\mathrm{km}}{1.496 \times 10^8~\mathrm{km}} = 4.65 \times 10^{-3}$$ and its mean angular ... • 18.7k 3 votes ### How to find how many degrees from the beginning to the end of the sunset? The easiest way to measure the sun would be to use a pin-hole camera. Use a piece of card with a pin hole. Hold it up so the sun shines through the pin hole and onto a piece of paper. (Don't look at ... • 123k 3 votes ### Meaning of$\cos H\$ in the rising and setting formula

The problem is not with the spherical triangle. A triangle can always be formed between three points on a sphere as long as the three points are not on a great circle. (The three points are the ...
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### math tool to compute time of sunrise and sunset

The rise and set equations below are from Astronomical Algorithms, and the approximate Sun position is from the Astronomical Almanac. The rise/set algorithm works for any celestial object given it's ...
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### Why is moonrise/moonset before sunrise/sunset on some days but after on others?

While one sunrise to the next is about 24 hours, one moonrise to the next is about 24 hours and 50 minutes. The extra 50 minutes are due to the Moon's orbit about the Earth. It therefore shouldn't be ...
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### Seeing a star near zenith around sunset

Is that possible? Yes! You can see bright stars and planets through a telescope in the evening and in some cases during the day. As magnification increases the brightness of the sky or any extended ...
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### How to calculate sunrise and sunset on on a given date and location?

Assuming you mean this in practical sense: Just use one of the numerous free websites that give this data: Eg. https://keisan.casio.com/exec/system/1224686065 Assuming you want to know about the ...
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### Timing based on upper or lower part of sun/moon

It is the first one, i.e. as soon as the heavenly body can be first seen. Here a definition from http://www.ga.gov.au/scientific-topics/astronomical/astronomical-definitions Sunrise is defined as the ...
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