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Questions tagged [astrometry]

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How do they know how far out Farout is? (2018 VG18)

The Carnegie Science article Discovered: The Most-Distant Solar System Object Ever Observed begins: Washington, DC— A team of astronomers has discovered the most-distant body ever observed in our ...
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1answer
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At what latitude could Orion's belt and Aldebaran be ~10 degrees above the horizon at the same time?

In his appearance on television contained in the video The Mystery That Keeps Neil deGrasse Tyson Up At Night, in the backdrop behind astronomer and educator Neil deGrasse Tyson and the talk-show host,...
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How can you estimate distance of an object by its redshift? [duplicate]

Is there a way to take the red shift of an object and, from that, calculate a rough estimate of its distance from us (in parsecs, preferably)?
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How to calculate the various properties of a star?

I am wanting to plot a velocity profile (a plot of velocity against the star's distance from the galactic core) from the Gaia DR2, but so far my efforts have been disappointing. The information I ...
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4answers
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Measurement uncertainty of the computed center of gravity from pixel image

Establishing the position of celestial bodies (stars, and other objects) is based on imaging technology. Depending on the resolution of the imaging sensor used, an object is identified by a group of ...
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1answer
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What are these “nonstandard format” lines in Distant Artificial Satellites Observation circulars?

Mike G's great answer clued me in on how to find the collection of astrometric observations of spacecraft which is maintained by the Minor Planet Center. I've noticed that there are nonstandard ...
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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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1answer
379 views

Where might astrometric observations of the Roadster spacecraft be catalogued?

above: (see small red lines near center of image) Tesla Roadster. 18 Feb. 2018, 11:28 UT. The image above comes from the average of ten, 300-seconds exposures, remotely taken with the 16”-f/3.75 ...
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How do you find the positions of celestial objects in the sky?

I want to write a program which, when given a date, a time, latitude and longitude, returns a list of the planets, Messier objects and NCC catalogue objects what are visible in the sky at that time ...
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81 views

Determination of High-Accuracy Distances of Terrestrial Planets from the Sun

I understand how in olden days the Sun-Planet distances were estimated using:- (i) measures of planet orbital periods ($T$) from analysis of observations over several centuries; (ii) Kepler's 3rd ...
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1answer
107 views

What resolution is needed to see a quasar through the galactic center?

The center of the galaxy is densely packed with stars and obscured by a whole lot of dust between us and it. For those reasons, groups that study the motion of stars around the super-massive black-...
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1answer
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Why does Sirius proper motion “wiggle” with a 1 year period, when Sirius A and Bs binary orbit is a 50 year period?

Some stars, if observed repeatedly over time, show a perturbation or "wobble" in their proper motion. If this is a periodic occurrence we can infer that the perturbation occurs due to the ...
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1answer
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How did ancient astronomers know to order the planets from the closest to the farthest from the Sun?

If we assume a geocentric model of the universe (like ancient astronomers did) how could we ever find out (again, like ancient astronomers did) the right distances of the planets? For example, how the ...
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3answers
577 views

Calculating the distance of objects using the Gaia DR1

The Gaia DR1 was released middle of September with ~1.1 billion objects. The schema contains right ascension, declination and parallax, which could be used to calculate Cartesian co-ordinates (xyz). ...
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1answer
106 views

What's the difference between GSR and Grf

I note there are two terms about Galactic rest frame in literatures: Galactic Standard of Rest (GSR) and Galactic Rest Frame (Grf). Are they the same frame? If not, what's the difference?
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342 views

Moving-Cluster method for determination of the distance of Hyades. A starter problem

I am currently following a class of observational astronomy lab. I will present a brief description of the method in first and then proceed to the question, so anyone is welcomed to read the entire ...
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2answers
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How was precision astrometry done before digital imaging?

Did they just put a ruler on the photographic plate? Quite some precision must have been required to discover Neptune from its influence on Uranus for example.
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Obtain tangent point (origin) of the Standard Coordinates system

In a previous question (Transform pixel coordinates (in FITS file) to equatorial), Rob supplied a great source that describes the process of obtaining celestial coordinates for objects in an observed ...
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1answer
327 views

Transform pixel coordinates (in FITS file) to equatorial

Say I have a FITS file with an observed field of stars, each one with x,y coordinates given in pixels. Assume the image is aligned so that the x axis is the right ascension, and the y axis the ...
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1answer
255 views

Open access table of visible stars with magnitude, coordinates, and possibly color?

I'm looking for a link to a table of visible stars that is open and available to everyone. It should have magnitude, RA, dec, and possibly some indication of color. This will be used to produce ...
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1answer
192 views

Angular distance/apparent separation between AE Aurigae and Orion's belt

The title perhaps gives the question away, but would anyone know/be able to roughly approximate the angular distance/apparent separation between AE Aurigae and Orion's belt. I have the value of $42^\...
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Tools and algorithms for angles-only orbit estimation

I've seen discussion threads where amateur astronomers estimate a satellite's orbital parameters from angles-only telescope observation. Are there any community tools or algorithms to help with this ...
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1answer
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I can't find Rigel on Tycho 2 catalogue

I'm trying to develop a planetarium using Tycho 2 catalogue. To read it I use the WCSTools. But I have a problem. On Wikipedia I have found that Rigel star has RA: 05h 14min 32,3s and Dec: -08º 12’ ...
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1answer
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Gaia: What is the difference between CCDs used for astrometry, photometry, and spectroscopy?

My knowledge of CCDs is that these are sensors which collect photoelectrons. That's about it. What is a difference between CCDs used for astrometry, spectroscopy, and photometry? As an example, each ...
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3answers
356 views

the initial astrometry calibration for a telescope

Generally a telescope can memorize how to point to a target with a particular RA&Dec. There is no need to calibrate every day. How can it happen? How to let the telescope(non-amateur) know the ...
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1answer
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Are astronomers continuously monitoring exoplanetary systems?

I'm reading many of the Wikipedia pages about exoplanets and the different methods they are using to detect them. But I wonder, it seems that the emphasis is on detecting and finding new exoplanets, ...
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347 views

If the Wow! signal was not directed at us, then where?

We probably all know the Wow!-Signal, happened on August 15, 1977. Assume that it wasn't meant for us. What was it pointing at then? The signal at that time came from RA= 19h25m31s ± 10s or 19h28m22s ...
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How does angular resolution of a telescope translate to its parallax precision?

We can often read in the scientific and also more casual reader literature and articles about the angular resolution of various telescopes and other optical equipment, be it ground based or onboard ...