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Hi all,

Just a thought. I've been examining the parallax method of calculating distances to stars in Parsecs for a science project, and I was wondering, any earth based observations made over the course of 6 months on either side of the earth's orbit around the sun would only be able to find distances to stars up to  about 100 Parsecs (326 ly). If that is so, what if you made the observation from a planet that is farther away from the sun thus having a bigger orbit (eg: Mars) ? would that increase the limit of distance measurable for a star? which way is better from Earth or from a location farther away? any advice or comments would be great!🙂

May the force be with you.

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Not only that - there would be an added bonus of smaller atmosphere impact!

There are a few problems that prevents us from very precise parallax measurements on earth - atmosphere, precision of tracking and so on ... All of those "smear" star image and add uncertainty in true star position (although we use centroid type algorithms).

Maybe best solution would be a space telescope / or pair of space telescopes in orbit around the Sun at some distance, maybe exploiting L points of some of outer planets?

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The 100 pc limit applies only to observations from within the atmosphere (parallax of 0.01 arcsec). The Hipparcos satellite (geostationary orbit) was able to measure distances accurately up to 500 pc, Gaia (in orbit around the Sun-Earth L2 point) even more.

Yes, observing from an orbit with a larger semi-major axis will increase the distance limit with the same error. Here's an interesting comparison of the parallax differences of Proxima Centauri as seen from the New Horizons space probe and from Earth.

Edited by Waddensky
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If you have time on your hands, you could wait for 120 million years. Then, the baseline, the diameter of the Sun's obit about the centre of our galaxy (about 60000 light-years), could be used for parallax measurements of distances to far away galaxies. 😁

I have been lazy, and I have not calculated if effects of the expansion of the universe would be noticeable with this method.

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19 hours ago, vlaiv said:

Not only that - there would be an added bonus of smaller atmosphere impact!

There are a few problems that prevents us from very precise parallax measurements on earth - atmosphere, precision of tracking and so on ... All of those "smear" star image and add uncertainty in true star position (although we use centroid type algorithms).

Maybe best solution would be a space telescope / or pair of space telescopes in orbit around the Sun at some distance, maybe exploiting L points of some of outer planets?

That's some interesting info! quick question. What exactly did you mean by "L points "? 

thank you again🙂🔭

May the force be with you.

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12 hours ago, George Jones said:

If you have time on your hands, you could wait for 120 million years. Then, the baseline, the diameter of the Sun's obit about the centre of our galaxy (about 60000 light-years), could be used for parallax measurements of distances to far away galaxies. 😁

I have been lazy, and I have not calculated if effects of the expansion of the universe would be noticeable with this method.

That would be awesome if you could actually do that! maybe if you build a time machine and take measurements now and go forward a 120 million yrs to take the next one!🤣🤣

May the force be with you.

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19 hours ago, Waddensky said:

The 100 pc limit applies only to observations from within the atmosphere (parallax of 0.01 arcsec). The Hipparcos satellite (geostationary orbit) was able to measure distances accurately up to 500 pc, Gaia (in orbit around the Sun-Earth L2 point) even more.

Yes, observing from an orbit with a larger semi-major axis will increase the distance limit with the same error. Here's an interesting comparison of the parallax differences of Proxima Centauri as seen from the New Horizons space probe and from Earth.

thank you for the great info! they were a great help. 😀🔭

May the force be with you.

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  • 2 months later...

Hello again everyone,

I am now in the process of completing the write up for my parallax project and I came across a question which I need an answer in order to explain my project. (google was no help cuz already tried that and couldnt find a correct answer😝

How do astronomers actually measure the parallax angle of a star? do they use any special equipment or do they calculate it mathematically? and can someone explain the equation d = 1/p which is used to calculate stellar distances in parsecs and how  it relates to the earth-sun distance and parallax angle? 

Edited by Anakin Skywalker
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I'm currently reading this https://www.amazon.co.uk/Parallax-Measure-Alan-W-Hirshfeld-ebook/dp/B00633W6L4/ref=mp_s_a_1_1?dchild=1&qid=1598867267&refinements=p_27%3AAlan+W.+Hirshfeld&s=digital-text&sr=1-1&text=Alan+W.+Hirshfeld which you will undoubtedly find interesting and useful!  It includes some details of methodology and the formula you asked about.

Best wishes for the write up 🙂

Helen

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