Questions tagged [horizon]

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Demonstration- formula for angle between horizon and ecliptic

The most precise and quite intuitive formula I could find online is here: https://www.celestialprogramming.com/snippets/angleBetweenEclipticAndHorizon.html $$\cos I = \cos ϵ \sin ϕ − \sin ϵ \cos ϕ \...
astrid lovespie's user avatar
3 votes
1 answer
120 views

New moon rise same spot on horizon as sunrise, almost same time [closed]

I witnessed the new moon rise just ahead of a sunrise at the very same spot on the horizon. How often could I plan on looking for that occurrence again?
Ruby Moseley's user avatar
5 votes
1 answer
324 views

Crossing of particle horizon and a past light cone

What does it mean when a light cone intersects a particle horizon? Like here, about 2 billion years after the big bang? Does it have any significance? I went through a few simple equations and the ...
Kontrola Faktů's user avatar
3 votes
2 answers
112 views

Small Angle Approximation Discrepancy in Horizon Dip Angle

Let's get back to the classic astronomical problem of calculating horizontal dip angle using small angle approximations. Let, our observer is a point object situated at an height $h$ on the earth ...
Rangan Aryan's user avatar
1 vote
1 answer
313 views

What is the relationship between the shape of the analemma and the sun's azimuth at sunset at a given latitude?

I want to know how the sun's azimuth at sunset changes over the course of a year. At first, I thought it would have purely sinusoidal motion, hitting its maxima and minima at the solstices, and ...
Greg's user avatar
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5 votes
2 answers
238 views

Can Mercury be seen from the 60th parallel north on Earth? Shetland, Faroe, Norway, St Petersburg, Alaska

I'm originally from a city in Spain which is 40 degrees north, and I used to watch Mercury (naked eye and telescope) every time I had the opportunity, that is, when Mercury was at maximum elongation ...
we'll see's user avatar
  • 305
3 votes
2 answers
74 views

Calculate viewing times at a location - when location has an obstruction

My most convenient viewing location is my backyard. It also has an obstructed view of the sky - trees. This means that just knowing the rise and set times of a planet does not let me know when, or ...
Bookaholic's user avatar
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0 votes
1 answer
75 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
4 votes
3 answers
1k views

Solar Azimuth angle Derivation

I tried posting this on math stack exchange to no avail so I thought maybe it's more relevant here : I know a similar question has been posted here before but no links to any mathematical derivations ...
aman's user avatar
  • 165
3 votes
1 answer
293 views

How to find the moons maximum culmination at a location

Forgive me if my terminology is incorrect, but is there someway or somewhere when I can calculate based on my location when the moon will be at the highest point in the sky overhead based on my ...
Matt Stewart's user avatar
1 vote
2 answers
2k views

A plot of the Moon-rise/sets on the Horizon Location

We have been trying to see where the moon rises/sets on the horizon. Unfortunately, the moon is not cooperating. Even when we know the moon rise/set times (timeanddate.com), we often cannot find ...
Bookaholic's user avatar
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2 votes
0 answers
62 views

Is there a more permanent way to set up an Artificial Horizon?

For the last few months we have been constantly setting up an Artificial Horizon (Davis Instruments) using motor oil as the liquid. We discovered that it is very hard to take a reading off of it ...
Bookaholic's user avatar
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1 vote
0 answers
467 views

Calculate position of sun in sky

I would like to calculate the angle formed by the sun and the horizon for any hour of the day and any day of the year for a particular place on Earth. So like: what is the angle of the sun to the ...
Mark Polczynski's user avatar
3 votes
1 answer
217 views

How to tell which of the ecliptic cross horizon angles is to the east?

Jean Meeus' Astronomical Algorithms, 2nd ed. p. 99 gives a formula for finding the two longitudes where the ecliptic crosses the horizon: $$\tan\lambda = \frac{-\cos\theta}{\sin\epsilon \tan\phi + \...
Shawn Lauzon's user avatar
1 vote
1 answer
183 views

How low can the sun be seen in the sky?

I'm interested in knowing how low the sun could ever get in the sky and still be seen. More technically: what's the minimum possible elevation of the sun at which it can still be seen above the ...
Wyck's user avatar
  • 391
1 vote
2 answers
108 views

What parameters cause sunburn? [closed]

I am new to this site so if the question doesn't fit in this forum feel free to remove it. I have read here https://en.wikipedia.org/wiki/Sunburn of all the causes of sunburn and I was mostly aware of ...
user29321's user avatar
1 vote
2 answers
242 views

Should the sun appear very low in the horizon if its path is always between the two tropics?

If the sun never rises above the tropic of cancer and never goes bellow (southern) of the tropic of capricorn then it seems that it should appear to the observer lower and lower in the horizon for as ...
Jim's user avatar
  • 263
2 votes
1 answer
593 views

How much more atmosphere is the sun passing through at sunset as opposed to at its peak in the sky?

I was looking at the sun during a sunset earlier today and wondered how much atmosphere you need to be able to look directly at the sun without damaging your eyes. The thought crossed my mind because ...
Magic Octopus Urn's user avatar
3 votes
2 answers
189 views

Is there any formulae to calculate whether the sun will depress 18 degrees or more below the horizon on a certain day / location?

I'm trying to code a piece of software which will calculate some times for me that would greatly help me in my day to day but none of my formulae work if the sun doesn't go at least 18 degrees below ...
15150776's user avatar
1 vote
1 answer
327 views

What could be past the particle horizon?

Forgive any kind of "dumb" question I may ask as this is a new interest of mine and I know it's purely hypothetical. If one were able to surpass light speed and the expansion of space to go beyond ...
CS2016's user avatar
  • 113
1 vote
1 answer
213 views

Has the velocity of photons coming from black holes already been measured?

Has the velocity of photons, which are coming from black holes, already been measured? I am not aware of such measurements. The reason for the question is the following: If space-time near black ...
Johann Weiser's user avatar
1 vote
1 answer
296 views

How long can you be trapped orbiting around a black hole for?

I have a story I wanna write but I want to be sure it's not completely scientifically irrelevant. I know there is black hole modelisation called the Kerr black holes, in which there is a limit ...
MarcelinDéter's user avatar
3 votes
1 answer
3k views

Why aren't all planets in the same plane?

Obviously all planets are not in same perfect plane. Because if at all they were in the exact same plane, it would mean that Mercury transits and Venus transits would not be that rare. Any ...
snoozemonster's user avatar
21 votes
2 answers
2k views

Are there any galaxies which fell out of sight horizon due to cosmic expansion?

If farthest galaxies run away from us with acceleration making them exceed speed of light, we should expect them to disappear from sky among time with increasing quantity. Did we observe this? Can we ...
Waldemar Gałęzinowski's user avatar
4 votes
1 answer
342 views

The furthest horizon in the Solar system

Where can I observe the furthest horizon in the Solar system ? And what the length of it ? The furthest horizon on Earth can be observed from mount Everest ~ 336 km, On Mars - from mount Olympus ~ 386 ...
user3715778's user avatar
5 votes
1 answer
1k views

Sun path at poles

At places other than the poles, the sun is seen to "rise" on the Eastern horizon and to "set" on the Western horizon. After a period of night, the sun "reappears" on the Eastern horizon. At the poles,...
SabreWolfy's user avatar
15 votes
3 answers
13k views

Would time go by infinitely fast when crossing the event horizon of a black hole?

If you were to fall into a black hole, my understanding is that from your reference point, time would speed up (looking out to the rest of the universe), approaching infinity when approaching the ...
Jonathan's user avatar
  • 4,355
54 votes
9 answers
11k views

Does matter accumulate just outside the event horizon of a black hole?

My understanding is that time slows and approaches stopping when approaching the event horizon of a black hole. I have seen this explained several places, including a brief explanation in the last ...
Jonathan's user avatar
  • 4,355
10 votes
2 answers
734 views

Can moon set after being up when due north? (pseudo circumpolarity)

I'm in the northern hemisphere, facing north, and notice that the moon is due north (azimuth 0) and is still above the horizon, albeit barely. Does this mean the moon is necessarily circumpolar (...
user avatar
15 votes
1 answer
2k views

Why does the Moon seem larger when it is close to the horizon? [duplicate]

I've noticed that when I look into the sky at night, sometimes the moon appears very large near the horizon. Sometimes it also looks like it has a yellow tint. Is this the light rays bouncing off ...
Timtech's user avatar
  • 1,703
15 votes
1 answer
857 views

Will an observer falling into a black hole be able to witness any future events in the universe outside the black hole? [duplicate]

I know someone or something sucked into a black hole could not survive, but is the bending of light so immense that an observer falling into a black hole will be able to witness any future events in ...
Timtech's user avatar
  • 1,703