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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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What does it mean that the Sun`s rotation axis is: RA 286.13° , Dekl: 63.87°?

first post here. I found 1 related Question, which has not solved my Problem. SHORT QUESTIONs VERSION: Suns axis is 7,25° tilted from the ecliptic. But in which direction? LONG QUESTION: Nasa ...
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1answer
43 views

angles on the celestial sphere

This is a somewhat simplified, and drawn / formulated in a manner more targeted to astronomy, version of a diagram and a question that I've also posted in math.stackexchange.com. In the diagram below ...
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2answers
42 views

Calculate position of the Sun in ECEF

I'm making a very basic orbit simulator in C# using the Helix Toolkit. I want to position the Helix lighting object at the sun, but also be able to calculate solar eclipse by the moon and earth for a ...
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1answer
23 views

Clarification on Greenwich Sidereal Time (GST)

I know that LST = HA + RA. And GST is LST + longitude(L). If a star culminates, it's HA=0. Therefore, GST = RA + L. Since RA and L are constants, GST must also be a constant. So, how can GST be ...
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Code for getting the pixel coordinates of an object with known RA DEC not working

I’m working on a project of which one of its functions is determining the XY pixel coordinates of an object given the object RA DEC coordinates and a platesolved image (this assumes that the target is ...
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1answer
41 views

Need help with the calculations/conversion of a celestial object

I'm developing a telescope controller open-source application. I started this project with a very little knowledge of Astronomy. Basically, the app is going to send data to telescope over a wireless ...
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2answers
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What are the RAs of the boundaries between traditional zodiacal signs?

I'm trying to figure out at what right ascension (RA) — not celestial longitude — the sun enters the various traditional (Western) astrological signs of the Zodiac; but I can't figure out how to ...
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Rotating azimuth/altitude to a focal point?

This is really a math question, but it's for use in astronomy, so: Because reasons, I'm writing my own sky-viewing code. I've found a few references for converting right ascension and declination to ...
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3answers
107 views

Differences between alt/az in Stellarium and Astropy

I've just started to learn Astropy. It's a nifty tool. Using some tutorials, I wrote and then made modifications to a little script that finds the Alt/Az of an object at a certain place and time. I ...
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1answer
26 views

Rising & Setting time of a star on a specific date

Given the local sidereal time (LST) of a star when it rises, how can I find out the time when it will rise (according to my watch) on a specific date?
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34 views

Rising & Setting of a star

Let the time required for a star to reach the meridian after rising be x and the time required for a star to set after crossing the meridian be y. Will x be equal to y?
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50 views

Calculation of RA and DEC

I'm currently stuck on a problem. I have the RA and DEC for JD2000: RA = 17 57 48.49980 DEC = + 04 41 36.1114 I want to calculate the RA and DEC for 01.01.2017, how can I do it? The solution ...
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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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3answers
117 views

Position of specific stars in the sky as a function of time

I'm a beginner in astronomy and I'm trying to figure out how to model the positions of stars in the night sky mathematically (ie a function which spits out azimuth and altitude as a function of time). ...
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1answer
44 views

Direction of movement sun with respect to the NGP

When viewed from above, i.e., looking down from the North Galactic Pole towards the South Galactic Pole, does the sun rotate clockwise or counterclockwise around the Galactic center?
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307 views

How to convert from Cartesian J2000 coordinates to Cartesian Galactic coordinates?

I'm using a star database (the HYG database) which has xyz positions and velocities for the stars. This has +X towards the vernal equinox, +Z towards north celestial pole, +Y towards Right Ascension 6 ...
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1answer
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Why are the spherical and cartesian galactic coordinates in the ATNF Pulsar Catalogue different?

I am trying to relate Galactic Latitude (b) and Longitude (l) (spherical coordinates) to galactic cartesian x,y,z coordinates in the ATNF pulsar catalog. This query shows some sample data with ...
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1answer
273 views

Convert Ecliptic to Galactic Coordinates

How to convert Ecliptic co-ordinates to Galactic? The wikipedia article on Celestial Coordinate systems contains various conversions, but this one is currently absent. For a more specific example: I ...
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Unsure how to obtain galactic roll?

I am having some issues with understanding what my adviser means by "galactic roll," but I have not been able to find anything online regarding this. My project involves generating an array of az/el ...
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42 views

How to convert planets coordinates to a person point of view?

I am trying to write a software (similar to Stellarium) that shows the positions of the planets, Moon, and Sun on the sky as you would see them standing on any place (lat/long) on Earth. I have been ...
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1answer
71 views

Given a star's ra, dec how can I compute one pair of lat, long and time where the star would be at zenith?

As the questions says, I have the celestial coordinates of a star(ra, dec). My trigonometry is not so great so I haven't managed to figure out a solution to this. I want to find a place (lat, long) ...
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1answer
531 views

ECEF to ECI conversion

How to perform the conversion of (r,v) vector from ECEF to ECI (J2000) coordinate frame? What I tried I multiplied the matrix ([cosA -sinA 0] [sinA cosA 0] [0 0 1]) by the state vector, where A is ...
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1answer
219 views

Coordinates of known black holes in our Galaxy (Milky Way)

There are some articles in wikipedia with the list of known (or candidates) black holes here and list of nearest black holes. Also there is a map of Milky Way. My question is where can I get ...
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2answers
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Measuring misalignment between two positions on sky

Let's say I have the (RA,Dec) for two positions on the sky. I want to measure the position angle between these two positions. In other words, if I had the Cartesian coordinate vectors for these two ...
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2answers
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Does anybody know how to get Sun-Jupiter Lagrangian points L4 and L5 RA and Dec?

I wanted to point at the L4 and L5 of Sun-Jupiter to find Trojan asteroids but I don't know how to calculate the RA and Dec of these. Do you know of any software that does it for you or how to ...
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1answer
396 views

Calculating Local Sidereal Time [duplicate]

When calculating local sidereal time, 100.461 "is the value needed to yield the correct value of GMST" - David Hammen (left as comment on my previous question). How ...
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1answer
855 views

Local Sidereal Time

I am trying to understand how to calculate local sidereal time and have found the following formula: $$\text{LST} = 100.46 + 0.985647 \cdot d + \text{long} + 15 \cdot \text{UT}$$ Here, $d$ is the ...
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1answer
222 views

How to convert density from physical unit to comoving unit?

I am learning co-moving units and I am interested to see how the conversion works. If Hubble constant is assumed to be 0.7, then I want to convert 1gm/cm^3 into comoving unit. If I want to express ...
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2answers
98 views

Celestial Coordinates

What is the standard coordination system used to describe the location at a celestial object approximately due east and at an angle of 10 degrees above the horizon?
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41 views

What does Ptolemy mean by “a line drawn from the centre of the earth through the centre of the moon to a point on the ecliptic”

This is from a translation of Ptolemy's Almagest Hence it necessarily follows that the straight line draw n from the centre of the earth (which is the centre of the ecliptic) through the centre of ...
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0answers
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calculating paralax angle from observations

Say I have 2 records, in horizontal coordinates of the azimuth ($A_z,A_z^{'}$) and altitude ($\alpha,\alpha^{'}$) of the moon at the same time in two different places that are $\theta$ degrees apart (...
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Convertion from Equatorial to altazimuth coordinates [duplicate]

I'm trying to convert equatorial to altazimuth coordinates with an Arduino Mega. I used this website which explain how to do it : http://www.stargazing.net/kepler/altaz.html But when I compare my ...
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What is the abbreviation for solar time, hour angle of the sun?

I understand that the hour angle and declination can be abbreviated as (HA Decl), and rectascension and declination as (RA Decl). The hour angle of a star is of course zero hours at the meridian. The ...
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124 views

How was the galactic plane established?

As pointed out in this answer the axes of galactic coordinates are defined such that galactic longitude and latitude (0, 0) point toward the galactic center. But then the plane defined by galactic ...
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1answer
155 views

can you translate a GPS coordinate to a Galactic coordinate

I am a complete newbie to astronomy and all the related. So if i say something stupid i am sorry. But i was wondering if it is possible to translate GPS coordinates like the following: ...
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2answers
155 views

Converting FITS (NuSTAR) coordinates to WCS

I'm trying to convert some pixel coordinates I have into WCS coordinates, ideally into a WCS region for use in some further analysis. So far I've been able to load and parse a NuSTAR FITS file, do ...
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406 views

Stuck on how to plot a fits in galactic coordinates

I've been stuck with this problem for a while now and I don't want to give up yet. I want to plot some fits images in galactic coordinates, with the WCS module from astropy I get the world coordinate ...
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2answers
86 views

Specific word for the point of the terrestrial surface “under” a star or other object in the sky

The title says it : I am looking for the word to use for a point, located on Earth surface (maybe an hypothetical perfectly spherical Earth), that has the same coordinates as a specific star, and ...
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27 views

Any method to apply inverse TPoint model?

I have an automated telescope that I have written some software for. I am currently using TPoint to compensate for some of the irregularities of my system. However with TPoint you apply an offset (...
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1answer
42 views

How to find if a set of objects lies within a given resolution (5 arcsec) on a telescope?

I am new to astronomy and I was given the task of finding out if there are objects which can't be resolved by a telescope of resolution 5 arcseconds. I was given the values of RA and Dec of these ...
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2answers
132 views

How to deal with the celestial meridian?

The book “Foundations of Astrophysics” by Ryden and Peterson states that one measures azimuth in the horizontal coordinate system eastwards starting on the northernmost point of the horizon circle. ...
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1answer
134 views

Finding Asteroid Geocentric Longitude and Latitude

I started using the software that comes with Jean Meeus book Astronomical Algorithms. I am now using the updated code from naughter(dot)com/aa.html. I am able to calculate the heliocentric longitude ...
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3answers
381 views

Why is right ascension measured on a 24 hour scale rather than a 23 hours and 56 minutes scale?

From several texts I have read, I have learned that right ascension is measured on a scale of 24 hours. I understand that Earth rotates almost exactly 360 degrees relative to distant objects, which is ...
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1answer
89 views

Get visible galactic longitudes in astropy

I would like to know which part of the Milky Way is currently up. Preferably using astropy. The ingredients I have are the current time, and my current position on earth. How would I use these to get ...
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2answers
151 views

What kind of a visual trajectory would an asteroid have if it were to hit Earth?

Let's say that Peter has a set of superb telescopes and he's watching the sky every night, for 3-4 months. He may not know it just yet, but there is an asteroid heading towards Earth, on a crash ...
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1answer
260 views

Converting Earth Moon Barycenter coordinate to Geocentric coordinate

I have Earth Moon Barycenter coordinate (J2000) generated from VSOP2013 in Astronomical Units, ...
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1answer
135 views

360 degree equirectangular projection of all naked eye stars with precessional motion for simulating

For many years now I've been using Voyager sky simulator by Carinasoft. The projection selections are great, but Equirectangular doesn't seem to one one of them. Is there a program out there that does ...
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383 views

Algorithm to Calculate Local Sidereal Time

I'm writing a fun program that needs to calculate the right ascension of the zenith position at a given longitude and latitude. Since RA is equal to Local Sidereal Time, How would I go about ...
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1answer
255 views

Where and how to look up the coordinates and magnitude of the star in this occultation prediction?

The motivation for this question comes from this question. A star is named in the occultation prediction shown below, from AsteroidOccultations.com's News & Announcements for 2014 MU69 on ...
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148 views

Celestial navigation from scratch

Is it possible to establish one's longitude and latitude by observing the stars? Can you use observations of the stars to find the relative distance between two locations, which would be useful in map-...