

Ask HN: Is stereoscopic photography possible with telescopes? - houseofshards

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) ?
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ggchappell
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](https://en.wikipedia.org/wiki/Parallax)

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

[http://www.sunflower-
astronomy.com/index.html?http://www.sun...](http://www.sunflower-
astronomy.com/index.html?http://www.sunflower-
astronomy.com/Stereo_Images.html)

And the moon,

[http://lcni.uoregon.edu/~dow/Marks_photos/stereo_pairs/Apoll...](http://lcni.uoregon.edu/~dow/Marks_photos/stereo_pairs/Apollo_moon/Stereo_pairs_of_moon.html)

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

[http://astroanarchy.blogspot.com/2010/04/ic-1805-as-
stereo-p...](http://astroanarchy.blogspot.com/2010/04/ic-1805-as-stereo-
pair.html)

Some explanation of the artistic method,

[http://astroanarchy.blogspot.com/2011/02/sh2-132-as-
stereo-p...](http://astroanarchy.blogspot.com/2011/02/sh2-132-as-stereo-
pair-3d.html)

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brudgers
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.

