# Questions tagged [parallax]

Questions about the apparent displacement of a celestial body with respect to its background when observed along two different lines of sight.

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### Units in distance parallax relation

Relation between distance d and paralax plx is: $$d (pc) = 1 / plx(arc)$$ When I want to express plx in mas, will it be $$d (pc) = 1/[plx(mas)*1000]$$ or $$d (pc) = 1000/plx(mas)$$ Thank you very much
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### Measuring distance to stars - How to get parallax angle

This may be a bit of a noob question, but I am wondering how exactly to get the parallax angle in degrees when looking at a nearby star relative to background stars. I have found the information ...
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### Does the presence of dark matter in the Milky Way significantly distort our parallax based measurements of distance?

According to accepted astronomical wisdom, dark matter represents a large fraction of the total mass of the Milky Way. And thanks to Papa Einstein, we know that light rays can be bent when passing ...
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### vertical shift is equals to half of angular dimension plus parallax plus atmosphere refraction

I'm developing a C++ computer library with the formulas in the book "Practical Astronomy with your Calculator or Spreadsheet 4th Edition" but I have a problem with the formula 49, "...
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### Is it more accurate to measure distances from Mars?

I'm trying to figure out answer to this task: At a certain level of development of the Martian civilization, scientists of this planet began to measure distances. Will their measurements be more or ...
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### How to calculate the distance of "3C 147"

According to Simbad ( http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=3C+147 ), the parallax is 0.0471 which would put it at a distance of 69,249 Light Years by using https://www.translatorscafe.com/...
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### How 3’ minute arc error in the Sun altitude might amount to 7’ minute arc displacement in Sun's longitude?

In reading "The Error in Kepler's Acronychal Data for Mars" by Curtis Wilson 1969 (unfortunately , this is not an open article), we read the following paragraph: How did it come about that ...
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### How exactly was Giovanni Cassini able to measure the distance to Mars?

Recently learned that Cassini was able to calculate the distance to Mars quite well using parallax in 1671. I was surprised, since even at opposition of Mars, the parallax (with respect to the Earth's ...
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### How are SIMBAD's parallaxes calculated?

I've been trying to figure out how to convert parallax information from SIMBAD's database into parsecs. Looking at Wikipedia as well as many other sources, parallax is calculated as follows: ...
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### How to solve numerical problems based on diurnal parallax method (formulas, examples and calculations)?

In physics, I have to solve some numerical problems based on the parallax method. I learnt the parallax method from Khan Academy and Wikipedia. (I found a really helpful Khan Academy video parallax in ...
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### How to actually obtain the parallax angles that are used to determine distances of stars?

I’m trying to understand how to measure the distance to nearby stars using the parallax method. My question is: how do you get the value of the p angle?
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### How can I find the distance of the tower while standing at my roof?

Whenever someone starts telling about finding distances in astronomy, it all starts with a parallax. The example they give is straightening your hand and see how your thumb changes its location while ...
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### Using parallax to find distance to the moon

I want to use the parallax method (from scratch) to find the distance between the earth and the moon. To get a significant parallax, I need to choose a large baseline. I live in India and my friend in ...
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### Why is WISE J0521+1025's distance so uncertain?

If you look at the Wikipedia page List of nearest stars and brown dwarfs , you'll notice that all stars mentioned in the list have a very precise value; all are $\pm0.02$ ly (except for GJ 1005, but ...
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### Can New Horizons be used to measure the distance to Betelgeuse (despite its fickle photocenter)?

The New Horizons spacecraft is almost 50 AU from Earth and near-simultaneous images taken by its telescope and one on Earth have demonstrated parallax without relying on the movement of Earth in it's ...
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### When was the parallax of a star first measured?

Telescopes like Gaia measure the parallax of stars with a great precision. But for stars that are beyond 11 kpc, their parallax is still too small to be measured. With Earth-bound telescopes, only the ...
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### Calculating distance using plate scale to measure parallax angle - high school homework question

I need a reality check. All of the context around this question would take way too long to explain, but I'm perfectly willing if I haven't provided enough information here. I'm trying to figure out if ...
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### Measuring parallax angle, same local time or the same time

I was thinking about measure the distance to the moon using parallax angle. But I have a confusion. I have read couple of articles about that, but one thing is unclear. Should we take pictures of moon ...
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The abstract of A magnetar parallax (also in MNRAS) says: TE J1810-197 (J1810) was the first magnetar identified to emit radio pulses, and has been extensively studied during a radio-bright phase in ...
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### Does parallax measurement depend on position in the sky

Naturally, the parallax is easier to measure for stars that are closer than farther away. But if all stars were the same distance from the Sun, and if there were some other reference to measure the ...
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### Best way to simulate star sizes to scale in celestial sphere

Using the Hipparcos catalogue, I am trying to create a celestial sphere. As all the stars are a fixed distance from the centre of this sphere, the only way to differentiate the distances and magnitude ...
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### Do parsecs scale as an inverse proportion with parallax angle?

high school student here. In astronomy my teacher says that if the parsec angle ($\alpha$) of a star is 1/50 arcsecond, then that star is 50 parsecs away. I'm not really convinced - calculation of ...
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### 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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### What is the furthest star for which we can measure the diameter?

If a star is close enough that we can measure its parallax and that it doesn't appear point-like, then we can deduce its diameter. Can we measure the diameter of all the stars for which we can measure ...
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### How can the radius of a star be measured using parallax?

The radius of Betelgeuse was measured using parallax. From the Wikipedia article: the estimated parallax from the Hipparcos mission was 7.63±1.64 mas, yielding an estimated radius for Betelgeuse of ...
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### Can I use the parallax coefficients for observatories as a proxy for latitude using arctan2(sin, cos)?

In How are the three character IAU Minor Planet Center's Observatory Codes assigned? Why are some letters so popular? I looked at the distribution of the first alphanumeric character versus the value ...
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### What's the most distant object we've measured by parallax? [duplicate]

The openstax Astronomy textbook says that when the Gaia mission is complete, we'll have parallax measurements to 30k light years. Do we have those now? What's the most distant object astronomers have ...
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### Distance to Proxima Centauri (Gaia VS New Horizons parallax program)

The current best parallax measurement for the nearest star to the Solar System, Proxima Centauri, has been given by the European Space Agency's Gaia mission. This is $768.5004\; \pm \; 0.2030 \; mas$ (...
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### How could one use the transit of Mercury to try and find the Astronomical Unit?

I am trying to use the transit of Mercury to estimate the distance between the Earth and the Sun, or 1 AU. I know that I need to observe mercury from two antipodes, but I do not understand any of ...
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### Is Olbers' Paradox Nonsense? [closed]

Ok, this is a bold question, I know. But, let me explain: After first hearing about Olbers' paradox, I found that something seemed 'off' about it, so I looked into the subject as much as my skills (...
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### Syncing time for measuring the parallax of Mars

I read somewhere (I can't remember the website) that when Cassini and Jean Richer measured the parallax of Mars, they used Jupiter's (or maybe Saturn's) moons to sync their time. How was this done?
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### Tycho Brahe's model

Tycho Brahe made a model of universe where earth is at the centre and motionless whereas all other planet orbited around the sun. I am interested to know how he came to this model? If it is because of ...
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### How can GAIA's accuracy for position, parallax, and annual proper motion for a given star be the same number?

Per Wikipedia's Gaia (spacecraft); Objectives: Determine the position, parallax, and annual proper motion of 1 billion stars with an accuracy of about 20 microarcseconds (µas) at 15 mag, and 200 ...
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### What is the maximum distance measurable with parallax? [duplicate]

What is the furthest star or celestial object whose distance has been calculated with parallax and how does it compare to the theoretical limit using today's telescopes? And how exactly does telescope ...
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### Is there an optimum orbit for a Hipparcos/Gaia-like parallax observatory

The Gaia spacecraft is currently mapping the stars in the Milky Way by parallax. It orbits in the Earth-Sun L2 Lagrange point. The parallax observed from the spacecraft orbiting around the sun allows ...
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### Why no Polaris distance in GAIA DR2?

Querying GAIA DR2 for Polaris (for example using https://gea.esac.esa.int/archive/) yields empty parallax columns. Anyone knows why it was not measured/published?
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### What is the proper interpretation of a negative parallax?

The Gaia data release 2 dataset has some parallaxes listed as negative. What is the proper interpretation of this? Should they be discarded as bad data? Use their absolute value to calculate the ...
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### Open cluster membership determination via parallaxes

I'm working in my final course project and I'm using the recently released GAIA DR2 data. I want to determine open clusters membership and I know this has mainly been done using proper motions and ...
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### How does a Solar Transit give more accurate determination of Earth-to-Sun distance?

I understand how Solar Parallax calculation determines the Earth-Sun distance using measurements of (a) the baseline distance between two widely-separated terrestrial telescopes and the (b) two angles ...
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### Distance parallax and cosmological distance in universe in expansion

I know that we cannot measure cosmological distances with parallax, but this is more a philosophical question. Am I correct in assuming that if we could measure distances using parallax (like stellar ...
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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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### Saturn observation : how to calculate requirements for Parallax method

In September, Saturn is 9.9au away from Earth. If we use the parallax method, what should be the base line between the two people? So I know that $D = B / \theta$, but how do I find out theta? I'm ...
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### What's the farthest object as determined only by parallax?

I'm wondering what the farthest object we know of, as measured only by parallax methods, from either earth or satellite based telescopes, and at either visible light or radio wavelengths. Basically, ...
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### What was Bradley's observation concerning abevation of light?

As far as I understand, the effect of parallax exhibits itself in the shift of a star relative to the background stars on photographs. As for the aberration of light, how is it reflected? It would ...
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### Parallax due to the motion of the sun

Generally, the parallax is contributed to the motion of the earth around the sun. However, at the same time, the sun is moving too. It carries the earth with it. Presumably, the shift of the sun is ...
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### If a star orbited another star, how would that affect parallax measurements of the other star from the vantage point of the first?

Example: If hypothetically, the vantage point would move 2AU along an orbit around the star being measured, would that make it seem as if the other star moved twice the distance over the back-drop?
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### Stellar parallax

I am doing a project on "how astronomers measure distance" where i came about with stellar parallax. i realized how it works with trigonometry but i am having a slight doubt tan p=distance between ...
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### Could we parallax measure stars just based on the Earth's size?

Imagine two major surface observatories, perhaps the "northermost" and "southernmost" such (ideally on a similar longitude). For nearby stars, could they each take a photo at the same time, and ...
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### Gaia Parallax data

When the Gaia parallax data (especially for Cepheid stars) become accessible to public? If it is already released for some parts, where can I find it?
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