<p>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?</p>

CC BY-SA 4.0
2019-09-11T09:20:41.200Z
This is certainly on-topic here, but just fyi there is also [History of Science and Mathematics SE](https://hsm.stackexchange.com/) as well. If you don't receive an answer after some period of time, you might consider moving this question there.
uhoh
CC BY-SA 4.0
2019-09-11T14:57:24.633Z
Wild guess:  the angular separation  of these observers when, say, a Saturnian moon initates occultation is in the noise compared with their parallax when observing Mars.
Carl Witthoft
<history><time><parallax>
Syncing time for measuring the parallax of Mars
Arnab Chowdhury
# Syncing time for measuring the parallax of Mars

(Asked by: username_0 on 2019-09-11)

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?

**Tags:** history, time, parallax
> **Comments:**
> **username_1**: This is certainly on-topic here, but just fyi there is also [History of Science and Mathematics SE](https://hsm.stackexchange.com/) as well. If you don't receive an answer after some period of time, you might consider moving this question there.  
> **username_2**: Wild guess:  the angular separation  of these observers when, say, a Saturnian moon initates occultation is in the noise compared with their parallax when observing Mars.  

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## 0 answers

