Questions tagged [coordinate]

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

Filter by
Sorted by
Tagged with
21 votes
4 answers
6k views

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 ...
ALiCe P.'s user avatar
  • 1,017
19 votes
3 answers
10k views

Could someone explain RA/dec in simple terms?

The equatorial coordinate system isn't too complicated. However, for people new to this, it seems rather intimidating at first. Is there an easy way to explain it?
Manishearth's user avatar
  • 4,949
13 votes
6 answers
4k views

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 ...
J. A.'s user avatar
  • 133
12 votes
1 answer
11k 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 ...
user3574623's user avatar
12 votes
1 answer
1k views

Do stars of a galaxy change their positions relatively to each other?

Complete astronomy noob over here who would be happy if he get a simple answer (and who is also aware that this may be not possible)... I've learned from a tv documentary that the stars at the edge ...
MarMun's user avatar
  • 123
9 votes
3 answers
2k views

Coordinate system for space [closed]

I am high school student, I have doubt if I have to locate a planet or any star in space, how do I locate it, because we have no perfect coordinate system, I have read in some books, that time is ...
आर्यभट्ट's user avatar
9 votes
1 answer
4k 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 ...
bhjghjh's user avatar
  • 403
9 votes
1 answer
2k views

Given a date obtain latitude and longitude where is the sun zenith

Searching is easy to find terminator line (frontier between day and night) or the position of the sun in the sky given a position on the earth and a time; but I can't find how to obtain where is the ...
Black Cid's user avatar
  • 191
8 votes
3 answers
1k views

Determining latitude and longitude in bad weather

In Sobel's famous book 'Longitude', she described the story of Harrison. I still have one question. What if it is cloudy on the sea? In this case, the sailors have nothing to compare with, right? This ...
S. Kohn's user avatar
  • 879
8 votes
3 answers
13k views

How do I plot galactic coordinates using matplotlib and astropy in python?

I want to make a projection of millisecond pulsars on the galactic plane, much like this one from Sala et al. 2004: I have tried several methods, and have not gotten anywhere. This is my current ...
Maria's user avatar
  • 185
8 votes
2 answers
458 views

Planetary reference systems and time

I am researching into how coordinate systems of solar systems objects are created by reading some of the reports written by the Working Group on Cartographic Coordinates and Rotational Elements (e.g. ...
spk578's user avatar
  • 181
7 votes
2 answers
764 views

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 ...
2080's user avatar
  • 1,858
7 votes
4 answers
4k views

Need Simple equation for Rise, Transit, and Set time

I've been looking, unsuccessfully, for hours for a simple set of equations: Input: RA and Dec of an object Observers Lat and Lng Current Time Output: Rise Time Transit Time Set Time (and, ...
W. Christopher Moses's user avatar
7 votes
2 answers
579 views

Different times of sunset at the same location due to elevation

Me and my friend were watching the sunset on the same location (at my country the latitude is approximately 40 degrees). I am at sea level and my friend is at an elevation. He observed the sunset with ...
justaguest's user avatar
7 votes
2 answers
633 views

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 ...
user177107's user avatar
  • 2,669
7 votes
1 answer
3k views

Calculate latitude and longitude based on date and sun

I can't seem to find this algorithm, if it exists. Can you calculate the longitude and latitude of where you are standing based on the date and the angle of the sun? Also, would the algorithm work for ...
Aaron's user avatar
  • 179
7 votes
1 answer
789 views

Calculation of Horizontal Coordinates

Given a fixed coordinate location on Earth (i.e. a latitude and longitude), and a fixed equatorial coordinate location of a particular astronomical object in the sky (i.e. right ascension and ...
ruadath's user avatar
  • 243
6 votes
2 answers
7k views

Difference between J2000, FK5 and ICRS coordinate systems? Which one does the Yale Bright Star Catalog use?

I have no background in astronomy. I have been wanting to write code to make star charts for a given location and time, which led to this question. I figured out that I would need to convert the ...
Aayush Mahajan's user avatar
6 votes
1 answer
337 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 ...
uhoh's user avatar
  • 31.3k
6 votes
1 answer
1k views

Why is the symbol of Vernal Equinox ♈?

Since the direction of Vernal Equinox lies in the Pisces constellation, why is its symbol Aries? Shouldn't it be ♓ ? Is this a historical anachronism, only invalidated by axial precession of Earth?
SF.'s user avatar
  • 6,249
6 votes
1 answer
556 views

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 ...
I Love Math's user avatar
6 votes
2 answers
3k views

Why is right ascension measured in hours?

When viewing star maps in Stellarium, I noticed that the meridians of the equatorial grid were denoted in hours and not degrees, and that always puzzled me. Why did astronomers choose this system? I ...
Joe Z.'s user avatar
  • 163
6 votes
2 answers
6k views

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 ...
werdnerd's user avatar
6 votes
1 answer
260 views

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 ...
Jagerber48's user avatar
6 votes
1 answer
156 views

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 ...
DaG's user avatar
  • 161
6 votes
1 answer
3k views

Convert coordinates between RA/dec and WGS 84 (SRID=4326)

I've imported the HYG Database from http://www.astronexus.com/node/34 and now I need to convert all RA/dec stars positions to fit in a WGS 84 coordinates (SRID=4326) PostGIS map (-180 to 180, 90 to -...
Magno C's user avatar
  • 339
6 votes
0 answers
131 views

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", ...
JKrsl's user avatar
  • 121
5 votes
2 answers
161 views

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 ...
Particle king's user avatar
5 votes
1 answer
752 views

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,...
Questioner's user avatar
5 votes
1 answer
4k views

Is there a map of the galaxies?

I see that there are many maps of a single galaxy, the Milky Way, showing the positions of the stars within our galaxy. I could not find a map of Galaxies, however. Is there such a map? In lieu of ...
Tyler Durden's user avatar
5 votes
2 answers
855 views

Where is the North of the Universe

Does it exist North of the Universe? (Which is probably used for determining coordinates of far galaxies.) If so, then where it is? On what is it aligned? (Is it orientated on Earth, Sun, Milky Way, ...
User123's user avatar
  • 2,879
5 votes
2 answers
16k views

How to find Greenwich Mean Sideral Time?

I'm writing a program that converts position in the ECI (CIS, EPOCH JD2000.0) coordinate system to WGS 84 (CTS, ECEF) coordinates. To do so, I'm following what's described in this document and ...
Carles Araguz's user avatar
5 votes
1 answer
494 views

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 ...
Elena Greg's user avatar
5 votes
1 answer
614 views

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 ...
AviD1511's user avatar
  • 151
5 votes
2 answers
415 views

Data to "check" Kepler’s first law

I want to "check" Kepler’s first law by using real data of Mars. From the equation of the ellipse, I derived $$\frac{1}{r}=\frac{a}{b^2}+\frac{a}{b^2}\cdot\epsilon\cdot\cos(\varphi),$$ where ...
Joe_base's user avatar
5 votes
1 answer
2k views

Calculating RA/dec from JPL ephemeris data

I'm using JPL planetary ephemerides to calculate the position of planets. Using DE405 ephemeris (using a parser provided by Project Pluto with all tests passing). I am fetching the position of Mars ...
Nenad Vukicevic's user avatar
5 votes
2 answers
283 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 ...
gshepherd's user avatar
  • 101
5 votes
2 answers
778 views

Comoving distance between two points [(RA1, Dec1, z1) and (RA2, Dec2, z2)]

I have Redshift (z), RA and Dec positions for two points in a galaxy catalogue (say P1 = [<...
Ling Guo's user avatar
  • 151
5 votes
2 answers
3k views

Software to convert RA and DEC into ALT and AZ

I have implemented the formulas to convert AR and Dec into altitude and Azimuth in C++ following the book Practical Astronomy with your Calculator or Spreadsheet 4th Edition. In the book there is an ...
VansFannel's user avatar
5 votes
1 answer
2k views

Conversion between Astronomical Frames, ex. IRCF, FK5, FK4, etc…

I'm a little bit confused about reference frames, and I was wondering if someone could help clarify a few things? So let's say I have equatorial coordinates that refer to the mean equator and equinox ...
ashley's user avatar
  • 151
5 votes
1 answer
7k views

What part of the milky way do we see from earth?

When looking up at the night sky, we can sometimes observe a bright band of stars stretching across it. I know this is our galaxy but exactly what are we looking at? Could we look at the centre of ...
Jaywalker's user avatar
  • 163
4 votes
4 answers
896 views

Latitude, longitude and altitude of Ckoirama Observatory; where can things like this be looked-up?

This answer to Is Starlink 1130 (Darksat) really dimmer? links to the March 16, 2020 paper in arXiv First observations and magnitude measurement of SpaceX's Darksat which finds only a modest decrease ...
uhoh's user avatar
  • 31.3k
4 votes
3 answers
893 views

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 ...
quantumflash's user avatar
4 votes
3 answers
2k 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 ...
Rithwik Sudharsan's user avatar
4 votes
2 answers
209 views

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?
user avatar
4 votes
1 answer
2k views

Why do J2000 coordinates change with time in Stellarium?

I'm new to the field so I'm sure this is a basic misunderstanding. As I currently understand it, J2000 equatorial coordinates describe the position of objects by referencing a specific point in time (...
John's user avatar
  • 163
4 votes
1 answer
240 views

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 ...
DavidBriz's user avatar
4 votes
1 answer
146 views

Astronomical Term *Mezzocielo*

What is the name of the point of intersection of the great circle passing through the celestial north pole P and the Zenith Z, with the celestial equator? (Point T in the figure) In Italian this point ...
JustThinking's user avatar
4 votes
2 answers
1k views

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 ...
AstroDuck's user avatar
4 votes
1 answer
183 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 ...
Helen's user avatar
  • 399

1
2 3 4 5 6