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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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Error when calculating Alt/Az from Ra/Dec

I wrote a program based on this tutorial: http://www.stjarnhimlen.se/comp/ppcomp.html to calculate altitude and azimuth of a celestial object. When I compare the calculated RA/Dec values to the ones ...
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1answer
115 views

Is it possible to define a state of zero absolute angular momentum anywhere in the universe?

Conservation of angular momentum doesn't seem correct to me. I think this because radiation is present everywhere, no space is completely void, and no object perfect. Thus all objects will have uneven ...
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1answer
114 views

How to construct a sky map

First of all, I have very basic knowledge of astronomy so sorry if I make some mistakes in my terminology. I'd like to plot the Southern Cross. I can find the name of its 5 stars. Also, I have some ...
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1answer
73 views

Heliocentric distance from galactic x y and z coordinates

How can I get heliocentric distance to a star when I have galactic x y and z coordinates known ?
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38 views

Generate an uniform distribution on the sky between limits

I have an analog question of this one : Generate an uniform distribution on the sky I generate an uniform distribution on the sky, but just a patch of it, with $$\alpha_{min} \leq \alpha \leq \alpha_{...
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1answer
85 views

What are the problems that need to be taken in consideration when trying to find planetary position by using jpl ephemerides?

I'm currently trying to determine the position of the sun and the moon from jpl ephemeris DE200 which is referred to the dynamical equator and equinox of 2000 and uses tdb time. I am using the j2000 ...
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1answer
68 views

Formula for sun's atmospheric refraction below the horizon

I have searched in Google and found interesting articles for atmospheric refraction influence on sun's elevation above the horizon (from 0° till 90°). eg. Bennett G.G. etc. I would like to know if ...
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1answer
62 views

Given sunrise, noon, sunset, longitude and latitude can I calculate the “hight” or “ascension” of the sun?

I'm trying to make a simple app for my own use to be able to check which of my favorit restaurants have outdoor seating sun and for how long etc. Given the data in the title (sunrise, noon, sunset, ...
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1answer
56 views

How could I determine what areas of the Milky Way will be visible?

There is a new moon on Saturday, and the forecast in my area of Winnipeg, Manitoba, Canada calls for clear skies on that night. I would like to take a widefield astrophotograph. I have no idea what ...
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1answer
4k views

How far do we have to go to leave the galaxy?

How far is the sun from the edge of the galaxy in the following directions? Moving along the shortest path parallel to the galactic plane (outward radially) Moving along the longest path parallel to ...
3
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1answer
141 views

If the earth was not tilted, what would be the north star?

What is earth tipped toward? The simple answer is Polaris. The axis (one end of it) points at Polaris, so that's what it's tipped to point at. But when we saw "toward" what do we mean? When it is ...
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1answer
224 views

Will time that moon crosses meridian always be periodic?

If I observe the moon pass my celestial meridian at a specific north polar clock 'time' will I observe every subsequent passage at ( 'current time' + 13.2* X 'days passed' mod 360* ) ? Does the moon ...
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1answer
165 views

What should be the declination of a star to be marginally circumpolar given the latitude & height from ground?

If I'm given the latitude, I can easily find the declination by using declination = 90 - latitude. I can also find the angle of dip from the height but should I add or subtract it from the declination ...
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1answer
51 views

Calculate NEO object position with nasa Near Earth Object data

I wish to create a 3D visualisation of NEO's by date in relation to earth, but calculating their position at that time has got me stuck. From this question I was able to fine Nasa's NEO object data: ...
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88 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 ...
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3answers
847 views

Generate an uniform distribution on the sky

How to generate an 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 ...
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1answer
54 views

Measuring declination in negative hours of arc?

I'm running the program found at https://www.projectpluto.com/source.htm in order to find the Right ascensions and declinations of celestial bodies at various points in time. An odd thing I've noticed ...
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41 views

Calculate earth position (longitude and latitude) given the solar position [duplicate]

I have found how to calculate the solar elevation and azimuth given a particular latitude and longitude. I have been able to work backwards to get latitude, but I am having trouble calculating the ...
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1answer
187 views

How to visually chart HORIZON ephemeris

I'm trying to build a 3D model of the Sun, Earth and Moon in in Javascript (using Three.JS, which relies on x,y,z coordinates for all objects) in order to simulate the Aug. 21 eclipse. I've ...
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39 views

Zenith's and horizon's projection onto an equirectangular sky chart

When watching an online introduction into positional astronomy by Viken Kiledjian (https://www.youtube.com/watch?v=XsvAdRZ8MAM&list=PL2yn_e5rlIW0bsNIOc3dEadJ6YwTOoj-Z&index=9&t=1704s) my ...
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3answers
71 views

What of the following moon-situations would be better?

Okay, so imagine that there is an Earth-like planet, with the following conditions: It's further from it's sun than the Earth is from the Sun (not much, but enough for weather to be a little colder ...
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23 views

Ellipsoidal or geoidal height is taken into account when correcting for sunrise/sunset times

I would know which elevation is meant when one would correct for the elevation of a location on the Earth by calculating the times of sunrise/sunset. The value of -0.833 degrees is adopted for ...
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1answer
76 views

What is the difference between ICRS and ICRS2?

When I first learned about Positional Astronomy (50 years ago), everything was described with respect to the Equator and Ecliptic (true or mean, of date or of a specific epoch). Then 'they' invented ...
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52 views

Does an algorithm exist that takes an image of the night sky and tell you where in the milky way that perspective likely originates? [duplicate]

In Stargate they talk about using the stars on other planets to figure out their location. I know that's fiction, but it made me wonder if such an algorithm (with arguably little usefulness right now) ...
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1answer
178 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 ...
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2answers
253 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 ...
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1answer
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 ...
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1answer
185 views

About the formula for taking in count of the observer altitude in sunrise/sunset formula

I'm new here and searched for solution but did not found one. I have found algorithms in order to calculate sunrise and sunset times for an observer on the surface of Earth with explanations of ...
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1answer
291 views

How the position of this black hole known?

How do scientists know the positions of black holes? Observe the highlighted area in the image:
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2answers
236 views

Declination of the Sun formula

I encountered a book discussion that defines the Sun's declination as 23.5 degrees (inclination of Earth's equator to the ecliptic) times the sine of the Sun's longitude. Does this make sense? How do ...
3
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1answer
200 views

Length of a tidal day or by how much is the Moon late each day?

A tidal day is the MEAN time between successive meridian transits of the Moon. (This is sometimes called called a lunar day, a term that should be deprecated for use in this sense, because it is also ...
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0answers
52 views

Attempting to determine astronomy values in a parameter file

Recently I inherited quite a few old QuickBasic programs which perform various astronomical calculations. I'm attempting to understand these programs and rewrite some of them in Python. I do not ...
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1answer
86 views

Centre (projected) of a galaxy cluster

A galaxy cluster consists of somewhere around a few tens to several hundred galaxies. To measure the position of a galaxy cluster, i.e. it's RA and DEC, do astronomers always assume it to be its ...
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1answer
192 views

Is this a real picture of the moon?

I found this picture and I am really wondering if it is possible for the moon to get as close to the earth as this picture shows? ( Super moon above Rio De Janeiro)
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1answer
2k 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 ...
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1answer
289 views

Moving-Cluster method for determination of the distance of Hyades. A starter problem

I am currently following a class of observational astronomy lab. I will present a brief description of the method in first and then proceed to the question, so anyone is welcomed to read the entire ...
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2answers
336 views

Question on Equatorial and Galactic coordinate systems

I'm currently working with proper motions and have needed to convert my galactic longitude and latitude into right ascension and declination (ie from galactic to equatorial coordinates). This is fine ...
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2answers
85 views

Are Wikipedia's sun ecliptic-coordinate formulae accurate?

I'm creating a C++ program that calculates the ecliptic coordinates based on the formulae from Wikipedia But, my calculations appear off. The mean anomaly for today, for example, should be 80.4-...
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2answers
571 views

Solar / lunar positions in ECEF using SOFA C libraries

I'd like to calculate the positions of the sun and moon in the ECEF coordinate system using the SOFA (http://www.iausofa.org/current_C.html) libraries given a Julian day input. So far, I've got this ...
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0answers
50 views

Latitude and Longitude from Right Ascension and declination angles [duplicate]

Given Declination and Right ascension(RA) of Sun ,How can I calculate the position of sun in terms of Earth's Latitude and Longitude(Or the vector from Centre of Earth to Centre of Sun will pass ...
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1answer
88 views

SDSS. Google Sky and DeCaLs

(1) Please go through following image Possible Super Red Giant? However sdss shows it as galaxy! Am I missing something. (2) Google Sky shows object in latitude and logitude format like this. Is ...
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1answer
134 views

Angular distance/apparent separation between AE Aurigae and Orion's belt

The title perhaps gives the question away, but would anyone know/be able to roughly approximate the angular distance/apparent separation between AE Aurigae and Orion's belt. I have the value of $42^\...
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2answers
970 views

Where can I find/visualize planets/stars/moons/etc positions?

What resources are available to find the positions of planets, stars, moons, artifical satellites, asteroids, and other heavenly bodies?
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2answers
387 views

Why do stars seem not to move relative to each other?

Whilst I understand why stars move across our skies,(Earth rotation) I struggle to understand why they do not appear to move relative to each other. To explain: Take the best know constellation the ...
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1answer
245 views

Obtaining stars vector position in relation to the center of the galaxy at a given date

How can someone obtain such vector, for stars in the Milky Way? Input should be star data (from a catalog, eg: Hipparcos) and Julian Date. Output should be a Vector Position (in pc) in relation to ...
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2answers
777 views

Get date and time by position of the sun and the observer position

I am working on an astrology project (don't panic, my question is about astronomy or math), where I need to figure out some values by the longnitude of the planets. I have a program for this, the ...
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1answer
145 views

Where can I look up the 3D positions of the closest stars? [duplicate]

The problem: I want to simulate a travel from Earth to the closest 15-25 stars. Which is the fastest way to accomplish this? What i have: I currently have the distance between Earth and the nearby ...
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1answer
193 views

relation between azimuth angle of the sun and angle of the shodow

What is the relation between azimuth angle of the sun the bearing of an vertical object's shadow? For example if the bearing of the shadow is 75° can we conclude that azimuth angle of the sun is 195°?...
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1answer
746 views

Finding a location using the direction of shadow, UT and date approximately

Does anyone know how to find a location by using : the direction of shadow relative to the normal (for example azimuth angle) the Universal time (UT) and date I have a satellite image and I know ...
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1answer
169 views

Can we draw a min(distance) and max(mass) relation based on current observation data of nearby astronomical objects within several parcsecs?

The data precision now can exclude a >>$1M_{\odot}$ black hole companion, which has a, say 10000 year orbital period with our sun? Can we draw a two dimensional diagram(Mass VS. distance) to show the ...