Questions tagged [twilight]

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14
votes
1answer
532 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 ...
3
votes
1answer
235 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, ...
2
votes
2answers
84 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?
2
votes
1answer
69 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 ...
1
vote
0answers
18 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 ...
0
votes
1answer
49 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, ...
0
votes
0answers
29 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 ...
0
votes
0answers
56 views

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 ...