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Questions tagged [twilight]

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Website to calculate sun elevation on a certain day?

Is there a website that will calculate a chart of the sun's elevation over the course of a certain day? Something like this:
AndreKR's user avatar
  • 113
2 votes
0 answers
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Calculation of twilight sky surface brightness based on object's apparent magnitude

I would like to be able to compute the sky surface brightness, which is based on the object's apparent magnitude. We have formulas, which allow us to compute the sky surface brightness based on the ...
Geographos's user avatar
1 vote
1 answer
218 views

How close can Venus be to the sun in the sky and still be visible to the naked eye?

Assuming no artificial light, what is the minimum number of degrees apart would the sun and Venus have to be during the beginning of civilian twilight for the planet to be visible to the naked eye to ...
Bob516's user avatar
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2 votes
0 answers
38 views

Is there any way to determine when the brightness of twilight is equal to the brightness of the full moon?

Using the Netherlands for the location, assuming no artificial light, is it possible to determine how far below the horizon the sun would have to be for twilight and the full moon to equally ...
Bob516's user avatar
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3 votes
1 answer
261 views

Solar eclipse impact on twilight

Has anyone observed the impact of the solar eclipse on twilight? I mean mostly the extension of the totality path in the atmosphere. I mean the pattern below: I - normal situation with total solar ...
Geographos's user avatar
1 vote
0 answers
44 views

What magnitude stars are visible during a quarter moon, during nautical twilight?

Assuming I'm looking for stars at least 50° from the quarter moon, is there any way to determine what magnitude stars would be visible to the naked eye, in a sky without light pollution, during ...
Bob516's user avatar
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0 votes
0 answers
61 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 ...
patchie's user avatar
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0 votes
1 answer
86 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, ...
Reckless Glacier's user avatar
2 votes
2 answers
639 views

Is astronomical twilight always seen when the sun is 18 degrees under the horizon?

Is astronomical twilight always seen when the sun is 18 degrees under the horizon or are there other factors that may influence it?
Reckless Glacier's user avatar
3 votes
1 answer
316 views

Significance of astronomical twilight

What is the significance of astronomical twilight? Astronomical twilight is when "the geometric center of the Sun's disk is between 12 and 18 degrees below the horizon" , but what, if any, ...
Erik Vesterlund's user avatar
2 votes
1 answer
480 views

what degree in the sky does the sun change color?

I would like to know at what angle in the sky the sun changes from a white yellow to orange and red. I know that after sunset it's considered twilight until 18° beneath the horizon. So how many ...
Peyton Hanel's user avatar
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How does the Astronomical Twilight depend on the night length or the day length?

Some references say that the Astronomical Twilight starts at the last 1/8th of the night length, so it is long in Winter and short in Summer; But by using the 18 angle (sun elevation below the ...
geek11's user avatar
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14 votes
1 answer
582 views

At Mars' equator how long does twilight last?

With Mars' thinner atmosphere I'm assuming twilight would not last as long compared to the duration on Earth. Has there been any determination of the length of twilight on Mars at the equator or any ...
Bob516's user avatar
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