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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2
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1answer
77 views

Latitude of given altitude of Sun

From Question #6 of USAAAO First Round 2018 (1 point) For the following problem find the range in which the answer lies: on the day of summer solstice, on which geographic latitude is the sun ...
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Are there any *client-side* JavaScript astronomy libraries? (not node.js)

Are there any client-side JavaScript astronomy libraries? Almost every library I see appears to be server side for node.js. I realize some node.js libraries can be adapted for client-side use, so I'...
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1answer
403 views

Galactic Coordinate System and distance

If the Galactic Coordinate System is made up of two values, angles of longitude and latitude, how is distance measured? If you have those two values, you get a line from the sun in a certain direction....
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82 views

ra for sun vs stars

There is formula for stars sideral time: $$ra - \arccos(-\tan(dec)*\tan(lat)).$$ where $ra$ - is right of ascension at the vernal equinox. $lat$ = latitude $dec$ = declination Is it applicable ...
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1answer
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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 ...
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1answer
1k views

Calculating Angular Distance

Given the horizontal coordinates of two objects in the sky, how does one go about calculating the angular separation between them?
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1answer
73 views

Could someone please explain to me how I can extract velocity component values from Stellarium, for a given planet?

For a project that I am currently working on, I would like to know how one could extract velocity component values ($v_x$, $v_y$ and $v_z$) for a planet from the Stellarium software. The current ...
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44 views

IAO 2015 Question 1 Noon at the Olympiad

Yesterday, on October 16, 2015, the upper culmination of the Sun at the venue of the Olympiad was at 11:29:44 local time. Calculate as accurate as possible at what time the upper culmination of the ...
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1answer
43 views

Data in measures paper

What do this data mean please? http://cdsads.u-strasbg.fr/cgi-bin/nph-iarticle_query?1904AnOBN...8a...1N&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf
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1answer
64 views

Sky from Equator at 8,000 years Before Present?

The Stellarium software allows future views of the sky. I need an online resource (planetarium projector?) that shows pre-historical views, and from the Equator at 8,000 years before the present.
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1answer
136 views

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 ...
3
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1answer
126 views

VSOP for exosatellites? (Io, Titan, Ariel, etc)

VSOP87 (and the subsequent VSOP2000 and VSOP2013) provide reasonably accurate planetary positions while still maintaining a small file size compared to the Chebyshev polynomial files. VSOP ...
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1answer
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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 ...
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2answers
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How should I think about sunlight for the purposes of analyzing the angles it makes w/ earth?

Most diagrams I see of sunlight look like something like this: . They show that for basic geometric analyses, the sun's radiation can be thought of as 'thin lines' that strike earth. Further, at an ...
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1answer
155 views

Can Eight Retrograde (seen from Earth) planets occur?

First of all, for the purposes of this question Pluto is a planet. So the eight planets being considered are Mercury, Venus, Mars, Jupter, Saturn, Uranus, Neptune and Pluto. My question is: can all ...
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1answer
115 views

Is the longitude assigned to sunspots spherical or projected?

Sunspot maps are created from a projection of the sun, so the coordinates of sunspots (or active regions in general) are assigned according to it. Do these coordinates correspond to actual spherical ...
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evaluate solar eclipse Besselian elements? [closed]

I found this NASA website which says that to predict eclipse, we should solve the Besselian elements ..what does this mean, how can I solve for Besselian elements? Is there a numerical method? I need ...
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67 views

How to calculate planetary positions hundreds or thousands of years ago

Wondering how to calculate the following in a general way: Sunrise/sunset Equinoxes/solstices Moon phases Planetary positions For hundreds to thousands of years ago. Wondering what the calculation ...
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2answers
479 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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2answers
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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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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?
2
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1answer
106 views

Geographical Point of the Sun

I want to draw a Sun in a 3d scene, so I figured the easiest way would be to calculate the latitude and longitude of the point perpendicular to Sun position and then just move it "up". As a starting ...
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1answer
79 views

The Sun and Regulus together at the summer solstice

Viewed from Stonehenge, when did the Sun and Regulus rise together at the summer solstice? Also when did Regulus rise before the Sun and would have been seen before the dawn glare?
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1answer
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How to get the solar zenith from the longitude and latitude?

I have real data of “Direct Normal Irradiation” and “Diffuse Horizontal Irradiation” and I should calculate “Global Horizontal Irradiation”. I have also longitude, latitude and elevation. Could you ...
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1answer
67 views

Is there any star recognition framework/library available?

Being a daytime software engineer and a sparetime photographer, I was looking for a nice DIY project for the next weeks. I finally decided to build a star tracker with a camera mount, so that I can ...
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0answers
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Where on Earth can moon rise on the meridian?

Somewhat related to this my picture showing only diurnal motion but Moon—seen from Earth—has a rapid motion with respect to the inertial celestial sphere, unlike stars and planets. Its motion relative ...
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Is Spherical Astronomy by W. M. Smart a good book on positional/spherical astronomy?

I'm a math undergrad, but I'm really interested in learning positional astronomy; However, the only well-referenced textbook I've come up with is Spherical Astronomy by W. M. Smart. I would like to ...
3
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1answer
164 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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2answers
209 views

How do I make a custom pulsar map?

I'm looking to make a custom pulsar map like the one on the Voyager Records, but for an arbitrary location within the Milky Way Galaxy. I'm not even sure where to begin.
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2answers
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Angular speed of a planet across the sky

Assuming circular orbit, the evaluation of the angular speed of a planet around the Sun, just requires its orbital period. Similarly, to calculate its angular speed relative to the Earth (also seen ...
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2answers
117 views

Synodic period of planets

Many books explain the difference between synodic and sideral periods. The synodic period of planets are tabulated for centuries and it is defined as the time interval between two consecutive ...
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1answer
115 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
576 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
123 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
173 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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43 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_{...
3
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1answer
148 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
64 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 ...
18
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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
257 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 ...
2
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1answer
381 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
306 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
60 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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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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1answer
311 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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2answers
1k 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 ...
3
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1answer
205 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 ...
3
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1answer
311 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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3answers
1k 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
113 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 ...