# Questions tagged [coordinate]

Questions on systems to uniquely determine position of a point or other geometric element on a manifold such as Euclidean space.

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### How to get coordinates and brightness of all stars from 1 constellation on SIMBAD?

I would like to get the RA and DEC coordinates and brightness data of all stars in the Orion constellation from SIMBAD. I am attempting to do a 'criteria query' but I'm confused about how to sort the ...
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### Why are the sky distributions of SDSS DR16 and DR16Q different?

I've downloaded the csv files for SDSS DR16 and DR16Q and made a map of their sky distributions: The coordinates come from: DR16: RA_ICRS and ...
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### How does a black hole look like independently of coordinates?

Observing a black hole from far away, far it looks as if infalling matter accumulates on the horizon. If one falls in though, there is no horizon at all (or it always stays in front of you). Which ...
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### How can you derive equations between the Horizontal and Equatorial system if the two systems have different centers?

This might be a dumb question. If the center of the celestial sphere is the center of the earth, and the center of the horizontal system is the observer, why do people use this diagram to derive ...
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### Celestial coordinates of every pixel in the image

I am solving starfield using Astrometry.net, an amazing piece of software I must say. After solving the starfield, Astrometry gives celestial coordinates of centroids of every star in the image, as ...
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### Plotting galaxies in 3-D

Suppose I have a catalogue of galaxies in a .dat file with each row representing information about a galaxy: right ascension of the galaxy, declination of the ...
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### Celestial Coordinates and Sun's degrees below horizon

I am struggling to understand the how the coordinates work. Example: At vernal equinox RA=0 DEC=0, Does this mean the Sun is at its highest point at the equator? If my mean solar time is 2h 30min, ...
1 vote
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### Angle to the line of sight

I don't understand this angle used in galaxy clustering. There is the line of sight and this angle to the line of sight which is not clear to me. Here is a transcript of a description from 1705.05442: ...
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### Measure the deprojected distance between two points?

I have an image of a protoplanetary disk, from which I would like to measure the distance of various points from the centre. See below image for an example, where I would like to measure the distance ...
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### Azimuth and Altitude angle between two points in the sky

I want to know how to correctly calculate altitude and azimuth difference, separately, between two points in the sky. The same way will be with icrs coordinates. For the altitude difference, I simply ...
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### Airy's Water Filled Telescope: help required to fully understand the calibration procedure followed

I am reading/studying the instrument description of Airy's Water Filled Telescope (Airy, G. B., "History and Description of the Water Telescope of the Royal Observatory, Greenwich", ...
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### What is the relationship between true anomaly and solar longitude?

So, my ultimate objective is to map solar longitude values onto a pseudo-Gregorian calendar. I thought this would be simple, but it has turned out to be anything but. I have asked several questions on ...
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### Doubt about a computation in Jules Verne

In his Aventures de trois Russes et de trois Anglais dans l'Afrique australe (The Adventures of Three Englishmen and Three Russians in South Africa), Jules Verne describes in some detail the geodetic ...
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### Convert Earth-centered coordinates to rotating libration point (RLP) coordinates?

I'd like to plot the path of an object near L2 (like the Webb space telescope) in a rotating libration point coordinate system. That makes it is easy to distinguish halo orbits from more general ...
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### What's the Right Ascension & Declination of Galactic Left & Galactic Right?

For the purpose of being able to align my model to the galactic plane, I want to know the directions of the galactic center, anti-center, north, south, left & right. This gives me the answer for ...
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### What is the maximum latitude from which a satellite in a geostationary orbit around Saturn would be visible to an observer on the planet?

This question is part astronomy and part mathematics. I'm aware it involves “basic” trigonometry, but my brain is short-circuiting. From my calculations, the distance from the center of Saturn where a ...
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### Horizontal and equatorial coordinate systems

What is the difference between horizontal and equatorial coordinate systems apart from the notations (azimuth, altitude) and (right ascension and declination angle)? Please provide some measurements ...
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### TESS sector of observations in RA/DEC vs lat/long

I'm trying to figure out WCS & just generic astronomical coordinates system, in order to better understand/use TESS data. I've been reading the mit docs, but I can't understand the reasons for ...
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### What is the connection between declination and latitude?

The celestial equator is a projection of the terrestrial equator on the celestial sphere. So doesn't that mean the geographical latitude and the declination will be "exactly" equal, as they ...
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### What is a "valid" coordinate system?

I was reading "Natural Coordinate System in Curved Spacetime" by Ying-Qui Gu. The first sentence of the abstract struck me (bold emphasis added by me): In this paper we establish a ...
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### Converting a Satellite's position in Lat/Lon/Alt/Time to RA/Dec

I'm trying to convert a satellite's position given in latitude/longitude decimal degrees, altitude in meters, and time in milliseconds since epoch to right ascension and the declination. I have found ...
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### Where is it possible to observe the Moon for 24 hours?

I wrote an astronomy olympiad yesterday and there was one task I couldn't figure out an answer to: Estimate at what latitudes it is possible to observe the Moon for at least 24 hours. Under what ...
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### Mathematics for Conversion between ICRS and AltAz

I am writing some software, for my own learning experience, to convert astronomical coordinates to different frames of reference. An example of this would be conversion between ICRS which a lot of ...
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### At what time of the day of autumnal equinox the Sun's equatorial coordinates reach max value?

I'm trying to solve this task: At what point in time of autumnal equinox day, at sunrise or sunset will a) the declination of the Sun b) the right ascension of the Sun reach the maximum value? I'm ...
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### Altitude of Polaris is latitude

How to prove geometrically that the altitude of Polaris is equal to the latitude? I have seen in handouts that the altitude of the pole star gives the latitude of that place.
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### What is the Sun's absolute direction called?

Like the Sun's direction relative to the local standard of rest is called "solar apex" What term can I google instead to find info about the Sun's direction relative to the CBBR? I ...
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### Given a location and a time on another planet, how do you determine how many hours before or after sunrise is it there?

I'm actually not so much interested in sunrise/sunset times. What I want to know is how to relate local planetary coordinates (e.g., planetary lat/lon) to, for example, heliocentric coordinates at a ...
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### How come I can point to two places with telescope and have the same coordinates?

Absolute beginner here. I read through the telescope manual, watched many videos, and got a pretty decent understanding of DEC and R.A. However, I don't understand one thing (where theory doesn't ...
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### How does the rock Simurgh Saxum (-25.32°, 4.05°) on 101955 Bennu define its prime meridian and serve as the basis for its coordinate system?

Spaceref's NASA's "Tour of Asteroid Bennu" Selected for Prestigious Computer Graphics Film Festival says: It's hard to imagine what the surface of asteroid Bennu might look like - it's ...
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### Understanding the constant 6.697374558 when finding GMST

I'm trying to understand the constant 6.697374558 mentioned in this question: The Astronomical Almanac gives an expression for approximate mean sidereal time, in hours: \mathit{GMST}=6.697374558+0....
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### Conventional units for astronomical object coordinates

I would like to know what the conventional units for identifying a celestial object (J2000.0) are. For instance, I am reading a paper in which they refer to object SDSSJ170013.70+400855.6; I am ...
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### What are the aspects does the moon differs between cities located on the same latitude?

What are the aspects does the moon (astronomical position and other astronomical aspects) differs between cities located in the same latitude? - For example: Seattle, Munich, Vienna, and Ulaanbaator ...
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### If I was in a coma and woke up at night in the desert, what knowledge would I know instantly and after 30 days?

If I was in a coma and woke up at night in the desert, what knowledge would I know instantly and after 30 days of observation? Can I figure out the general directions, i.e. where North, South, East, ...
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### Understanding the difference between local time and local sidereal time

I am currently attempting to understand different systems of telling the time: particularly, distinguishing local time (LT) from local sidereal time (LST). I understand that they often differ; despite ...
1 vote
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### What do these latitudinal and longitudinal lines and accompanying hours and degrees represent?

I'm a beginner in Astronomy. What do these latitudinal and longitudinal lines and accompanying hours and degrees represent (in blue: +12h , +11h.. and +45° +60°.. , in orange: +330° , +15°) ?
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### rotate right ascension, declination based on delta time

Assuming I was observing a source at a given right ascension $\alpha_0$ declination $\delta_0$ at a given time $t_0$ under a certain azimuth $A$ and elevation $a$ angle. If I now change my time to \$...
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### Conversion of Moon's Celestial Position (RA and dec) to Horizontal Coordinates [closed]

I'm currently attempting to calculate the equatorial sky position of the Moon for any given Geostatic position (longitude / latitude) for any given datetime. I have tested my altitude and azimuth ...
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### Can someone explain to me the TEME reference frame in defining orbital coordinates?

I am undertaking a project of developing a "surface station" for my desktop, which will track the position of different satellites as they fly overhead. I have zero background in ...
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### Is this how stars’ right ascensions correlate to planets’ longitudes on a 2d map?

This is my first ever online question, so please bear with me: I’m working on an A1-sized map of at least 100 of the largest solar system bodies (henceforth just called ‘planets’, ignorning the IAU ...
1 vote
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### Filtering local region in SIMBAD

I am completely new to astrophysics and currently writing a paper on Cepheid variables for high school physics. I would like to filter out all Cepheid variables in the local system which I would ...
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### Converting Invariable plane to J2000 ecliptic

I've been following the answer given by Mike G here: How to calculate the orientation of planets at current epoch to get planets to have the correct orientation in my program, but all the angles are ...
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### Coordinates in the Night Sky

I've learned about Orbits recently, and there are 6 orbital elements. Now, I've heard of three coordinate systems whereas, they can help you measure positions of stars in the night sky. The Altazimuth,...
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### What is a "fundamental location", and why is Mosting A defined as one for the moon?

The crater Mosting A was chosen to be the "fundamental location" for the Moon's coordinate system (latitude and longitude). But what exactly is a "fundamental location"? What does ...
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### What do these coordinates mean: MW - VP101 3° 12' 43.2'' S 5° 12' 39.6'' W?

I have a jacket with a tag that bears the label: MW - VP101 3° 12' 43.2'' S 5° 12' 39.6'' W When I looked it up, I discovered that these are the coordinates of the ...
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### Plotting Equatorial coordinates to X,Y plane (simulating telescope/camera view)

I would like to simulate a telescope camera view, projecting (RA, Dec) coordinate sets to a 2D plane. So effectively the need is to convert Equatorial coordinates to (x, y) coordinates, when we can ...
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### What is the longitude of the winter solstice for the various planets?

I am looking for data showing the longitude at which the various planets in the solar system reach their winter solstice. Where could I find this data?
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### Orbit of Luhman 16?

I am studying some binary stars and brown dwarfs. Some orbits are known and easy to find, like Alpha Centauri. However, when I look for the orbital characteristics of Luhman 16 (AB), I only get the ...
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### How to calculate longitude of Alcyone - η Tauri in the year 41050 BCE?

Using the following information from The Skylive, and simple arithmetic I tried to calculate longitude of Alcyone in the year 41050 BCE at a place: 29.9457 N , 78.1642 E. Galactic Longitude 166.67°, ...
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### 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 ...
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