Ask HN: Is stereoscopic photography possible with telescopes? | Hacker News Reader

Ask HN: Is stereoscopic photography possible with telescopes?

Noob astronomy question: Imagine two telescopes photographing the same region of the sky (much like the human eyes). Can this help us perceive depth (distance from the Earth) ?

View on HN

Yes, that idea does allow for measurement of distances to astronomical objects. Sadly, to get decent measurements for things like stars, the two telescopes need to be very far apart -- farther apart than the diameter of the earth. But we can be clever about it; if we take a picture of a star and then take another one 6 months later, then the distance between the two positions we took pictures from is the diameter of the earth's orbit around the sun -- around 300 million km (while the diameter of the earth is less than 13 thousand km).

That allows measurement of the distance to nearby stars. For most stars, though, even 300 million km isn't far enough.

From Wikipedia[1]:

> Astronomers use the principle of parallax to measure distances to the closer stars. Here, the term "parallax" is the semi-angle of inclination between two sight-lines to the star, as observed when the Earth is on opposite sides of the sun in its orbit. These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder.

[1] https://en.wikipedia.org/wiki/Parallax

Here are some stereo pairs of Mars, Jupiter, & Saturn,

http://www.sunflower-astronomy.com/index.html?http://www.sun...

And the moon,

http://lcni.uoregon.edu/~dow/Marks_photos/stereo_pairs/Apoll...

Here are some artistic (not real) stereo pairs of the Heart nebula,

http://astroanarchy.blogspot.com/2010/04/ic-1805-as-stereo-p...

Some explanation of the artistic method,

http://astroanarchy.blogspot.com/2011/02/sh2-132-as-stereo-p...

One of the empirical phenomena that reasonably supported a geocentric cosmology was the absence of observable parallax in regard to the stars. It just points out that interstellar distances are vast beyond ordinary human experience...which is to suggest the concept of distance becomes a mathematical abstraction and untethered from the way we think about distances in our daily lives.

Reply on news.ycombinator.com