Questions tagged [positional-astronomy]

Questions about positions of objects in the sky, either relative to a fixed coordinate system like the equatorial and ecliptic coordinate systems, or relative to an observer's point of view.

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42 votes
2 answers
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Where can I find the positions of the planets, stars, moons, artificial satellites, etc. and visualize them?

What resources are available to find the positions of planets, stars, moons, artificial satellites, asteroids, and other heavenly bodies?
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12 votes
2 answers
589 views

Is it possible to figure out your location in the Milky Way if you are suddenly wormholed to a random, distant location in the galaxy?

If you were flying along in your spacecraft somewhere in our solar system and then a large, stable wormhole suddenly opened and you flew into it and were whisked away to some distant location in the ...
Arbutus's user avatar
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10 votes
4 answers
3k views

Generate a uniform distribution on the sky

How to generate a uniform distribution of stars on the sky ? What I want is make a simulation of random points following uniform distribution on a part of the sky (making the assuption that we have ...
Richard's user avatar
  • 331
8 votes
1 answer
4k views

What is the Galactic Latitude and Galactic Longitude? How is different from the latitude and longitude we use on Earth?

It has to something with the positioning of sun and galactic center of the milky way but I wasn't able to understand how for a given star, its co-ordinates are calculated. Some explanation would be ...
Amogh Mishra's user avatar
6 votes
0 answers
239 views

Viewing "Diamond Fuji"

Diamond Fuji is a phenomenon in which the (typically) setting sun is positioned directly atop Mt Fuji. Some relatively detailed predictions for viewing times at a nearby park are available here. I ...
kyle's user avatar
  • 161
4 votes
1 answer
358 views

Stellarium simulation

I'm interested lately in Stellarium and the functionalities which it provides especially scripting. I want to make a simulation that shows the celestial sphere with some planets like Venus, Mars, and ...
pourjour's user avatar
  • 141
2 votes
4 answers
230 views

consider you are stranded in deep space, and an alien agreed to drop you back home, how would you explain the location of earth in the galaxy? [closed]

remember they have no concept of what humans have named stars and clusters
jacolot329's user avatar
2 votes
1 answer
162 views

Calculating Position of Sun in GPS Frame Relative to 0°00'00.0"N 0°00'00.0"E: Determining Vernal Equinox Offset

I am trying to calculate the position of the sun, in GPS coordinates terms, from a given date. As of right now, I know how to accurately calculate the equatorial Right Ascension and Declination, and ...
Michael Bonnet's user avatar
31 votes
1 answer
4k views

If dark matter bends light, how do we know the stuff in the sky is where we think it is?

We measure movement, position, and many other things of an object in space because of its light and what we can measure with it. But as far as I know there's supposed to be a HUGE amount of dark ...
Sebastian Araneda's user avatar
10 votes
2 answers
2k views

JPL Horizons - "highly accurate measurements of planetary positions" - how do they do it?

According to JPL Horizons, with regard to their planetary position calculations, ... we integrate the equations of motion in Cartesian coordinates ($x,y,z$), and we adjust the initial conditions in ...
Peter's user avatar
  • 1,033
9 votes
2 answers
1k views

How was the First Point of Aries measured in ancient times?

According to Wikipedia, usage of the Sun's position as the basis for a celestial coordinate system dates back at least to Babylonian times, and the current "First Point of Aries" system ...
Greg Miller's user avatar
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7 votes
3 answers
908 views

How/where to check where the Sun is (constellation)?

I would like to check in which constellation the Sun was in at some time in the past, any recommendations how to do that?
user7549's user avatar
7 votes
1 answer
1k views

Planets positions (azimuth, altitude) API

I'm looking for a simple API that will allow me to get positions of planets and the moon for a given date, location and time. Does anyone know an API like that? Any suggestions or alternatives would ...
Deathbat219's user avatar
6 votes
2 answers
549 views

Tips of Crescent

Can it be shown mathematically that the line connecting tips of crescent is parallel to the North-South line and the line gives latitude of the plane ( When the Moon is sufficiently close to the ...
Particle king's user avatar
5 votes
3 answers
3k views

How can I convert my sky coordinate system (RA, Dec) into galactic coordinate system (l, b)?

I am an astro-particle physics PhD student trying to look for a simulation. I was looking for a conversion formula for sky (or celestial or Equatorial) coordinate system using Right Ascension and ...
Kyle's user avatar
  • 127
5 votes
1 answer
2k views

Straightforward derivation of the sunrise equation

I'm looking for a reasonably straightforward derivation of the sunrise equation$$\cos\omega=-\tan\phi\tan\delta$$as referenced in the Wikipedia article here. I've dipped into Astronomical Algorithms ...
Peter's user avatar
  • 1,033
4 votes
2 answers
2k views

What are the correct positions or alignment of planets in relation to each other and the Sun, is it vertical center, baseline or completely random

From a lot a illustrations and videos, the planets seem to align in vertical center to each other like this: Is this really true? I like to imagine that the planets are actually in weird alignment to ...
ifeoluwa king's user avatar
3 votes
2 answers
212 views

The Jupiter Effect Book

This evening I have been thinking about the anxiety caused in 1982 by predictions in John Gribbin and Stephen Plagemann 1974 book The Jupiter Effect. I was a teenager in 1982. The planets aligning ...
doctorsundar's user avatar
2 votes
1 answer
1k views

Help with Converting Right Ascension and Declination into 3D Vectors

Using the Right Ascension and Declination values from the HYG Database from The Astronomy Nexus: Right ascension is measured in hours and declination is measured in degrees. 1 - Convert right ...
SidS's user avatar
  • 225
2 votes
1 answer
146 views

On what four dates dates do we observe the minimal, maximal, and two days of zero Solar axial tilt relative to us?

In case the title is a bit confusing, what I'd like to know is essentially respectively on which dates the Solar axial tilt is pointing straight towards Earth, straight away from Earth, and ...
Outis Nemo's user avatar
2 votes
1 answer
401 views

Where can I get J2000 epoch initial mean longitudes for all planets and celestial bodies?

I'm following this paper to calculate geocentric coordinates. The authors have provided the initial mean longitude values for the planets (provided in attached table) for 01.01.2000 @ 00.00 UT but I'...
skiventist's user avatar
2 votes
2 answers
1k views

Jean Meeus - calculating moon rise, transit and set times - help isolating error in logic

I've been working my way through the Jean Meeus Astronomical Algorithms book for a few weeks, to implement some of the key algorithms for a personal project. This task has been a little more complex ...
Stew's user avatar
  • 21
2 votes
1 answer
119 views

About coordinate systems and angle differences

If I want to measure the beam-width of a radio telescope sweeping through a ~ puntual object (the Sun) with a ~ constant flux output when measured: The value measured sweeping in one frame of ...
nuwe's user avatar
  • 769
1 vote
1 answer
244 views

Translating a zenith position to the nadir

What would be the easiest way to translate a zenith position to a nadir on the celestial sphere? For example I have a position from the azimuthal grid in Stellarium; 3h44m32.64s/+50°50'16.2" ...
user36093's user avatar
  • 179