If we focus the telescope on the moon or some other celestial body, we no relief will not notice. This was to be expected, for the heavenly distances are too big even for stereo-telescopes. What are 30 to 50 cm, which are separated from each lens of the device, compared with the distance from the Earth to the planets? If it was possible to construct the device with the distance between pipes in the tens and even hundreds of kilometers, and then he wouldn't give any effect when observing planets distant from us tens of millions of kilometers.
Here again comes to the aid of stereoscopic photography. Suppose we photographed some planet yesterday and then again today; both pictures are taken from one point of the Earth, but from different points of the solar system, because during the day the Ground was time to move on orbit for millions of miles. Pictures, of course, will not be identical. And if these pictures you put in a stereoscope, you will see not flat, but the relief image.
We can, therefore, taking advantage of the Earth's motion in its orbit, to take pictures of celestial bodies with two very distant points; these pictures will be stereoscopic. Imagine a giant with a giant head that the distance between his eyes is measured in millions of miles, and you will understand what extraordinary results are achieved astronomers with the help of sky photos.
Stereoscope use at the present time to discover new planets, namely those minor planet (asteroid), which in many circling between the orbits of Mars and Jupiter. More recently, the study of them was a matter of pure luck. Now enough stereoscopically to compare two pictures of this part of the sky, obtained at different times; stereoscope immediately selects the asteroid, if he has taken on the sample, as it will be from the General background.
The stereoscope is captured not only the difference in position of the points, but the difference in their brightness. This gives the astronomer convenient way to find the so-called variables stars, periodically changing its luster. If two images of the sky a celebrity came varies strikingly, the stereoscope will immediately indicate to the astronomer that was changing its luster star.