Questions tagged [equinox]

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4
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2answers
77 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 ...
3
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0answers
67 views

How to calculate planetary positions hundreds or thousands of years ago

Wondering how to calculate the following in a general way: Sunrise/sunset Equinoxes/solstices Moon phases Planetary positions For hundreds to thousands of years ago. Wondering what the calculation ...
1
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3answers
231 views

Why is the equinoxes only 2 days and not more?

The earth is tilted at 23.5 degrees which means that in the solstices the north/south hemisphere is more radiated by the sun and the tilt to the sun is maximum. In the equinoxes, the tilt is not ...
3
votes
4answers
191 views

Is the equinox Sun always at the same zodiac sign in the ecliptic belt?

During the year the Sun moves along the ecliptic passing all the signs of the zodiac belt, in my understanding. This means that it takes ~1 month to go from one zodiac sign to the next. The ...
2
votes
1answer
59 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 ...
1
vote
1answer
66 views

Are the stars seen at the equator different throughout the year?

If you live on the equator and look up at the night's sky at, say, midnight, would you see a completely different sky on the 1st of January than you would on the 1st of July? I assume you would as ...
1
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0answers
103 views

What is the great (platonic?) year? How could it be explained in laymen's terms?

How could a great year be explained in laymen's terms? According to the definition in NASA's Aerospace Dictionary it is a complete cycle of the equinoxes around the ecliptic that completes in 26000 ...
4
votes
1answer
163 views

Why is the time between equinoxes different?

The path of the Earth around the sun is described as being an ellipse, with the Sun being at one of the foci of the ellipse. Since an ellipse, by definition, is symmetrical with respect to the foci, ...
2
votes
0answers
77 views

What's a good model for the vernal equinox year? Can it increase forever?

Duncan Steel (2002) makes an interesting argument that the notion of year is (1) somewhat arbitrary and, more interestingly (2) one notion of year can increase while another decreases. His examples ...
0
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1answer
668 views

How was the time of equinox measured in ancient times?

In the book "The Crime of Claudius Ptolemy" by Robert Newton, on page 81, it reads as follows: When we measure the time of a solstice, we measure the time when the meridian elevation angle of the ...