# 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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### 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: ...
76 views

### 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 ...
68 views

### 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 ...
106 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", ...
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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 ...
91 views

### 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 ...
1 vote
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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 ...
159 views

### 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 ...
1 vote
68 views

### 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 ...
110 views

### 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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### 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 ...
1 vote
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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 ...
1 vote
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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.
1 vote
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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 ...
76 views

### 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 ...
132 views

### 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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### 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 ...
1 vote
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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 ...
1 vote
153 views

### 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....
141 views

### Time evolution data of the Great Red Spot on Jupiter?

Jupiter's Great Red Spot fascinates scientists for ages, so it does me. Where can I find a table (e.g. as CSV-file) with the time evolution of longitude, latitude, horizontal and vertical extension of ...
169 views

### How do I plot field of view of an earth-based observatory in Galactic Coordinates?

I would like to plot in Galactic Coordinate the sky field-of-view of an earth-based observatory (e.g. MAGIC). Something like this from Liu et 2016. I already know how plot source positions on a 2D ...
536 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 ...
1 vote
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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 ...
148 views

### 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 ...
1 vote
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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, ...
1 vote
118 views

### 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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### 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 (...
1 vote
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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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### 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 ...
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### Clarifications about distances in cosmology

I would like to get clarifications about some usual notions of distances in cosmology. First, is the comoving distance the current distance of objects whose light has been reached by us now, i.e. ...
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 ...
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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 ...
47 views

### 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 ...
575 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,...
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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 ...
1 vote
359 views

### 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 ...
202 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 ...