Questions tagged [coordinate]

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

31 questions with no upvoted or accepted answers
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How to get SOHO Satellite images' coordinates?

I'm working with images from LASCO C3 coronagraph I'm able to download pictures from LASCO C3 using this form https://sohodata.nascom.nasa.gov/cgi-bin/data_query Then, I want to do some analysis of ...
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508 views

Earth-Centered Earth-Fixed coordinates with respect to heliocentric coordinate system at vernal equinox

I am trying to calculate the position of a point on the Earth's surface with respect to the Sun's center at a certain date and time. For what I am trying to do it is OK to ignore precession of Earth's ...
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79 views

Is Nomad data heliocentric or geocentric?

I'm wondering if the data in star catalogues are heliocentric equatorial coordinates or geocentric equatorial coordinates. Also given the distance between stars compared to the distance between the ...
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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 ...
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Detect sources near image edge with python photutils

As my question suggests, I 'm trying to use a python library photutils in order to detect sources from MUSE cube. MUSE (Multi Unit Spectroscopic Explorer) is an ...
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320 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 ...
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105 views

Why do astronomers use the equatorial coordinate system that moves, instead of one based on fixed, distant stars?

As an outsider to the field, I am surprised to learn that astronomers commonly use the equatorial coordinate system, in which fixed stars are not actually fixed. Isn't that making life harder than it ...
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47 views

Eccentricity from Analemma

Can the eccentricity of a planet's orbit be found just from the analemma of its star? We can draw an analemma given the axial tilt and eccentricity, but how do we find the reverse? Note: I already ...
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63 views

Issue translating World Coordinate system to cartesian coordinate

I have two fits images from the WFC3 that I am trying to combine with a C# program. When I try to combine multiple images I don't think the values I am getting for my x/y coordinates (calculated from ...
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35 views

Why do default coordinates from IR-optical observatories are usually not trustworthy, while from radio interferometers they usually are?

I have noticed in my experience that the coordinate solution within the headers of default reduced images from radio interferometers are commonly trustworthy to the arcsecond or less. From IR and ...
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149 views

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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61 views

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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48 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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422 views

Coordinates reduction python

How can I calculate position (alt, az) of star for observer at some station (longitude, latitude) on specific date and time? I need full coordinates reduction with all elements included in calculation ...
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11 views

Using altitude, azimuth to determine a baseline vector?

I know the equatorial coordinates of a “beam” pointing from an Earth-based observer toward some distant star. I have converted those coordinates to altazimuth coordinates for that observer and a ...
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1answer
35 views

Horizontal to Equatorial Conversion - Code

Following this tutorial I have been able to convert from Equatorial to Horizontal Coordinates and am now searching for a way to do the reverse. I understand this kind of question has been asked and ...
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33 views

Determine distance to Moon after diurnal parallax?

So, I want to find the distance to the Moon/any body after performing the correction for diurnal parallax. Unfortunately, the resources I have do not cover how to do this. Is there an easy algorithm ...
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27 views

How to determine Az-El pointing of a telescope spiral scan?

I am writing a simulation of an automated telescope observation program. One part of this is to run a spiral scan pattern on and around objects of interest. I would like to tile this scan pattern so ...
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45 views

What exactly is a Right Ascension clock and how was one (mounted on a telescope) used in practice, historically?

@MikeG's answer to Why does this Lowell Observatory telescope have so many knobs? What do they all do? explains that item #6 labeled in the image there (and cropped version here) is likely to be a "...
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224 views

Calculating the range of visible Right Ascension and Declination from specific location + time

Given a specific date and time, and coordination of a location on earth, how can I calculate (myself, or using a python package) range of visible RA and Dec? For example (but I'm looking for a ...
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89 views

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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46 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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94 views

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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50 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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59 views

Is there an English translation of the Parisian Alfonsine tables

I'm interested in the Alfonsine tables published in Paris in the 1400s. I know there is an English translation of what survived of earlier Alfonsine tables from Castile, but that's not what I'm ...
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470 views

How to calculate planetary aspects at a stationary point?

I am using Jean Meeus book Astronomical Algorithms and the C software that comes with the book to calculate planetary data. I am comparing two planet's longitude to calculate the time when they are a ...
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59 views

Attempting to determine astronomy values in a parameter file

Recently I inherited quite a few old QuickBasic programs which perform various astronomical calculations. I'm attempting to understand these programs and rewrite some of them in Python. I do not ...
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27 views

Position Angle Relative to North

I am trying to find the position angle of a star whose Ra and dec are known. I have already looked at the 'Measuring misalignment between two positions on sky' question and answer, but the answer ...
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59 views

Transforming Galactic Coordinates in Cartesian with Distance

Lets say I have galactic coordinates of an object, l and b. I figured out that i can transform them to cartesian system using the formula: $$ \begin{align} X &= \cos(b)\cos(l)\\ Y &= \cos(b)\...
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72 views

Calculating angle between the sun and a perpendicular to earth given lon/lat & time

If you had your longitude/latitude, and the time/date, how could I go about working out the angle between your normal and the sun? At first I was doing a simplistic approach of assuming elliptical ...
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59 views

How can one determine the declination range of stars visible for a certain amount of time above a specific airmass at a certain location?

Let's assume you want to observe stars at Kitt Peak (32 degrees North) at an airmass above 2, for 2 hours (30 degrees of Earth rotation). My attempt: The angle between the zenith and celestial ...