Questions tagged [coordinate]
Questions on systems to uniquely determine position of a point or other geometric element on a manifold such as Euclidean space.
299
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Why is there a discrepancy between the difference in ecliptic longitudes as found with Skyfield when accounting or not accounting for precession?
I'm using Skyfield to calculate some ecliptic longitudes for various dates. I understand that the 0° point of ecliptic longitude changes based on precession due to being the intersection between the ...
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Why is there a discrepancy between ecliptic longitudes found with Skyfield and Astrolog for old dates?
Just to preface this, I know that Astrolog is software meant for astrology, which is pseudoscientific nonsense; however, I have a friend who insists on using it for certain astronomical calculations (...
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How to get the direction of the rotation axis of a celestial body using JPL Horizons?
When asking Horizons for ephemeris, it doesn't include the information of the rotation axis. Is there a way to obtain it?(may include calculations based on the given information)
And is there any way ...
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1
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Delta T used by US Naval Observatory
I'm trying to compare some eclipse calculations to that by the U.S. Naval Observatory, specifically, these results. One thing I just don't understand is how they come up with a Delta T of 72.8s. ...
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Gaia coordinates in J2000 as done by the CDS
So I'm interested in knowing how the CDS calculates the J2000 equatorial coordinates from the Gaia DR3 equatorial coordinates (that are given in epoch 2016.0).
For example, for the star HD 308819 = ...
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Is this description of ecliptic times correct?
I did a brief write-up as a pet research project to explore astro-geological calculation and visualisation for
Muslim prayer times. It's not meant to be authoritative (either scientifically
or ...
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2
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Calculate geographical location (latitude, longitude) from horizontal and equatorial coordinates, date and UT
Lets say I found myself in the middle of nowhere with small computer with some sort of offline astrometry engine (like locally installed astrometry.net). I have some sort of mount that precisely tells ...
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Current sources for astronomical equation coefficients
For a project I needed to implement some of the code to calculate the position of the sun and moon. To do this I'm using Meeus. Everything is working but in doing so I've started to wonder about the ...
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1
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Implementing polar coordinates correctly in solar system model?
I am working on a 2d solar system model using Python, but I'm unsure if my implementation of planet data is correct. I have the planet data stored in polar form (distance, velocity and angle), and I ...
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How to flatten 3d astronomical coordinates into 2d polar form in Python
I first asked this at Stack Overflow but got redirected here
I am making a 2d simulation of the solar system. For that you need a starting point for all planets. Right now I am storing that data in ...
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Correct longitude from longitude over 180°
Last week, one of my exercise tasks was about determining the an observer's position on Earth, when in their zenith is a certain star with known right ascension and declination. We were supposed to ...
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How to find the constellation in which the sun is located using the night sky map?
The following sky map was given as part of practice problems in my Astronomy course
The moon is in its first quarter phase. I am supposed to find the approximate date and time of the year in which ...
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1
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Difference in results between JPL Horizons and cspice (rust-spice)
I am calculating the apparent planetary position of planets using the cspice library (I am specifically using rust-spice, which is a wrapper of cspice in Rust).
when I calculate the same values in the ...
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7
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How to describe the Sun's location to an alien from our Galaxy?
Let's say you got to the planet orbiting other star in our Galaxy through the wormhole. You think that the travel was instant but you're not 100% sure and it is not exactly known. The planet is ...
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How to plot object on the map correctly
I am wondering how is it possible to plot the celestial object on the map I have attached if I only know following data:
16h 41m 41,24s
36° 27′ 35,5″
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Are the rotational axes of Earth and Mars parallel?
So I was stuck on a question involving the transformation of coordinates from geocentric to Mars-centric coordinates. The relative position of Mars and its orbital details are given. I thought that we ...
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How can non-earth-orbiting satellite coordinates be obtained by amateurs?
Just a few hours ago the moon-bound spacecraft Chandrayaan-3 was launched.
While it will orbit Earth for a few days, it is accelerating/changing its orbit often to prepare for the transfer to a lunar ...
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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 \...
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3
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Reverse polynomial model for reverse astrometry
I have a polynomial model that can transform pixel X,Y coordinates to standard $\xi, \eta$. This model looks like this:
$\xi/\eta = a_1 + a_2x + a_3y + a_4x^2 + a_5xy + a_6y^2 + a_7x^3 + a_8x^2y+a_9xy^...
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Satellite angular velocity at an angle
Suppose I am observing a satellite that is not at my zenith. I know the altitude(α) and azimuth(γ) of my telescope and I was able to get a relative angular velocity of the satellite.
Based on this ...
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Compute footprint of a region observed with EPIC-PN
Given the coordinates of an observation performed by XMM-Newton, is there a way to compute the coordinates of the limits of EPIC-PN's field of view?
For instance, observation ...
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2
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267
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Sky coverage plot using Python/Astropy
I want to recreate a plot where the area that is not visible from a certain point on earth (latitude and longitude) trough a full year. An example of this plots for example can be:
Where in white is ...
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2
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How to find the numerical positions of objects in the sky?
How do star locator applications such as SkyGuide, SkySafari and Stellarium get the current and future positions of
moons, planets, stars and artificial satellites in the sky?
Is there a public ...
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Discrepancies in the equations for converting Horizontal coordinates to Equatorial coordinates
Hello I am trying to convert my Horizontal coordinate system dataset into Equatorial coordinate system. However, it seems that all the information from the internet is different.
I will use symbols as ...
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If Sagittarius A* were used as a compass, where would its points be?
I know a galactic co-ordinate system exists already, but it's dependent on the position of Earth. What if Sagittarius A* itself were used as the centre of a compass? What objects would best define its ...
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Calculate declination of Galactic N. Pole given obliquity of Ecliptic, rt. ascension of Galactic N. Pole, & angle between Galactic & Ecliptic Pole
I’m trying to back-calculate a value in astronomy using spherical trigonometry. (This is not a homework problem, I'm retired).
Using the following formula, where δ = the Declination of the Galactic ...
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1
answer
245
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Drawing stars in a 3D space
I'm using the Galactic Coordinates to draw stars in a 3D space, but I don't know how to do it.
In the book "Practical Astronomy with your Calculator or Spreadsheet" I've found this:
Where:
...
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6
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1
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How exactly is UT1 measured/calculated?
Background: I am an atomic physicist so I understand atomic time pretty well. But I'm not an astrophysicist or astronomer and I know very little about astronomical measurements.
I am interested in ...
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How to calculate distance between stars?
I have data on nearby stars, including galactic coordinates and distance from Sun. And I have a dilemma.
In a story I'm writing, I have two starfaring alien civilisations. One originates from a planet ...
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95
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How to draw galactic coordinate grid?
For my story, I need a galaxy map with star positions in the galactic coordinate system. 2D with a view of the galaxy from above would be enough.
I have gathered data from Atlas of the Universe and ...
0
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61
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Convert from magnetic coordinates to true coordinates
I am working with the IGRF (International Geomagnetic Reference Field) model and from a journal article found here, I am able to compute the earth's magnetic field at any point in spherical ...
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Computing the sky coordinates using astropy
I need your help with an error I have been receiving while trying to obtain the sky coordinates using astropy module in python.
The code looks like the following,
...
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Transforming galactic coordinates in Cartesian coordinates better formula? [closed]
I found on your site a formula to make this conversion,
a person helped me to insert it in an excel of which I put you the link.
https://docs.google.com/spreadsheets/d/...
2
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1
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313
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Deriving orbital inclination from equatorial coordinates?
I wanted to ask if it's possible to establish a correlation between the observed equatorial coordinates of a Solar System planet, especially declination, and the planet's orbital inclination with ...
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Transformation of hour angle to azimuth
Converting Hour angle to Azimuth, is there a simple way to know which result is correct (as the formulas and the arccosine give various results shifted by 180° etc.), or does one just have to figure ...
2
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0
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From TEME to RA DEC
I am using the SGP4 python package to get the coordinates of satellites at a given epoch. The algorithm computes the positions (X, Y, Z) in the True Equator Mean Equinox coordinate frame (TEME). From ...
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Figuring out camera pitch and roll given RA and DEC of center of image, as well as lat,long of camera and time taken
What I am trying to figure out is how to get the camera pitch and roll, as described in this image (the green yaw line is where the camera sensor is pointing
if given a RA, DEC (of center of image,ie ...
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How to use astropy to join data tables based on sky coordinates?
I have 2 astronomical tables, from a fits file and a csv file, that look something like this
...
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1
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Mismatch between the equation of the equinoxes and the correction for a right ascension
I am studying about apparent and mean positions of Sun using quite old books: Astronomical algorithms (1991) and Explanatory supplement to the astronomical almanac (1992).
The question is about the ...
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Are the Vernal Point and the Autumnal Point two antipodal points on the celestial sphere?
Intersections of the elliptic and the equatorial planes on the celestial sphere are the Vernal Point and the Autumnal Point. Are these two points two antipodes on the celestial sphere of the Earth?
user47535
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Is the Vernal Point a fixed point on the sky?
The Vernal Point is a reference point in the Equatorial Coordinate System, from which R.A. is measured. My book says that the zero point of Right Ascension, i.e. the Vernal Point keeps moving in the ...
user47535
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Derivation: Formula for projection of sun's motion onto parallel of declination
Consider the projected angular velocity of the sun along a parallel of declination. I was told that it is $$\frac{\cos\varepsilon}{\cos\delta_{\odot}} \frac{d\ell_{\odot}}{dt} \tag{1}$$
where we let $\...
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How to determine errors in coordinates from SIMBAD error ellipse
How to determine errors in ICRS coordinates from the SIMBAD error ellipse, please?
Thank you
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Right ascension - Gaia vs Simbad
What is the difference between Right ascension in Simbad and Gaia Archive, please? How to convert the values? For instance, HD 37468: 05h 38m 42.0s vs 84.68652242854718 deg. Should not be these values ...
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Problem in converting equatoral coordinates to ecliptic coordinates
I would like to convert equatoral coordinates to ecliptique coordinates. I am following the source below:
Practical Astronomy with Your Calculator
The formula I am using is:
When I solve this example,...
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2
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Which mobile/computer application can help me understand celestial coordinate systems better? [closed]
I wish to understand Equatorial and Altazimuth coordinate systems much better. Any applications or softwares which can help me out with the same?
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Measurement unit of coordinate systems in astronomy
Nearly all of the coordinate system I have studied in Positional astronomy use the degree system. This makes me curious about why astronomers prefer degrees over radians as we know that Radian is a ...
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Astrometry and Geometric Distortions
CCD's are widely used for astrometry. Since a spherical surface (the celestial sphere) is projected onto a rectangular surface, the plate scale or pixel scale (approximated with 1/focal length etc) is ...
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