<p>Are you treating $\Theta$ as the only unknown, i.e.  you believe you know the baseline distance exactly?    If so, then  you compare your angular sighting of a distant star vs. Saturn with the same for the other observer.    The devil is in the error analysis.  Your two angles will be absurdly close to each other in magnitude, which means a very small error/uncertainty in value leads to a large error in the calculated distance $D$ to Saturn.    </p>

<p>You should find some first-year-level text on measurement &amp; statistical error analysis to get a better feel for the difficulty here.</p>

CC BY-SA 3.0
2017-09-21T12:57:40.987Z
2017-09-21T12:57:40.987Z
Carl Witthoft
<p>In September, Saturn is 9.9 AU away from Earth. If we use the parallax method, what should be the base line between the two people?</p>
<p>So I know that <span class="math-container">$D = B / \theta$</span>, but how do I find out theta?</p>

CC BY-SA 3.0
2017-09-21T11:36:35.530Z
Can you clarify what D, B, and theta represent?
JohnHoltz
CC BY-SA 3.0
2017-09-21T15:37:14.880Z
It sounds like you're trying to calculate both $B$ and $\theta$. In order to use the equation you've presented, you have to know at least two of the three.
zephyr
CC BY-SA 4.0
2024-10-07T12:02:08.950Z
While @user21 is right that it will be difficult, I don't get their 0.03 arcseconds. Saturn's diameter is roughly 10 times of Earths, so from opposite parts of Earth Saturn will be be seen with parallax of about 1/10 of its diameter. Saturn's angular size is about 19 arcseconds (in opposition), so the parallax will be about 1.9 arcseconds.
Heopps
<saturn><parallax>
Saturn observation : how to calculate requirements for Parallax method
whytho
# Saturn observation : how to calculate requirements for Parallax method

(Asked by: username_0 on 2017-09-21)

In September, Saturn is 9.9 AU 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?

**Tags:** saturn, parallax

> **Comments:**
> **username_1**: Can you clarify what D, B, and theta represent?  
> **username_2**: It sounds like you're trying to calculate both $B$ and $\theta$. In order to use the equation you've presented, you have to know at least two of the three.  
> **username_3**: While @user21 is right that it will be difficult, I don't get their 0.03 arcseconds. Saturn's diameter is roughly 10 times of Earths, so from opposite parts of Earth Saturn will be be seen with parallax of about 1/10 of its diameter. Saturn's angular size is about 19 arcseconds (in opposition), so the parallax will be about 1.9 arcseconds.  

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## 1 answers

### Answer by username_4 on 2017-09-21. Score: 2

Are you treating $\Theta$ as the only unknown, i.e. you believe you know the baseline distance exactly? If so, then you compare your angular sighting of a distant star vs. Saturn with the same for the other observer. The devil is in the error analysis. Your two angles will be absurdly close to each other in magnitude, which means a very small error/uncertainty in value leads to a large error in the calculated distance $D$ to Saturn.

You should find some first-year-level text on measurement & statistical error analysis to get a better feel for the difficulty here.


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