I hope you find this both interesting and fun.

Our binocular or 3D vision works by the fact the left and right eyes have a slightly different perspective on a scene. The differential parallax, whereby near objects are displaced more than far objects in the images seen by each eye, is processed by our brains into a 3D image. If two pictures, with these different lines of sight, are presented to our two eyes, the brain can also integrate them and produce a 3D image. Have you ever used a stereogram to look at two side by side images and resolve a 3D image? Or perhaps you've seen an autostereogram which is a single-image stereogram (SIS), designed to create the visual illusion of a three-dimensional (3D) scene from a two-dimensional image, as seen in the 3D books? This technique can be used without a stereogram using what is called parallel eyes. Using this technique each eye looks straight ahead at the two images side by side, such that the right eye sees the right hand image and the left eye sees the left hand image. A 3D image can be resolved between them. This can take some practise but is very rewarding if you can make it work. It is best to have the two images really quite small, ideally the centre of the image as far apart as your pupils, say 5cm (2") apart. Stare into space (ha ha), through the image and the 3D image will resolve in the middle. If you have your hand on the mouse on the corner of the image, drag to slowly increase the size of the image, without looking away and certainly not at the mouse :-D. You should be hold the 3D image as you make it bigger and easier to see. If you go too far you'll lose it.

So what does all that have to do with astronomy?

Gary Imm recently published a very nice image of the trio of galaxies NGC 5981, 5982, and 5985 in Draco.  
Gary's image: NGC 5981, 5982, and 5985 - Draco Galaxy Trio
As I looked at the image, of course, it looks 2 dimensional and all the galaxies look to be at the same distance. In Gary's write up, he describes the relative distances to the galaxies and the fact that the edge on spiral NGC 5981 is at 90 million light years and the other two are 140 million light years away. Once I read that I imagined the edge on spiral being closer, but wondered if there was a way to better envisage their relative distances. And so I set about try to create a 3D image whereby the relative distances could be clearer to the human brain.
Parallax depends on the separation of the two perspectives (eyes) on a scene. Clearly the parallax from our eyes is so small that all celestial objects appear to be 2D. To get a noticeable parallax and a 3D effect we have to seperate our eyes further. Some stars show a small parallax when the eyes are separated by the diameter of the Earth's orbit (300 million kms), but even then the parallax is small and the nearby objects are seen to move slightly against the background stars. This is how humans first calculated the distance to relatively nearby celestial objects, using trigonometry. I had to use trigonometry to figure out how far my two images would need to be apart to get a "decent" shift in Gary's image. With some trial and error, I worked out that to produce a 3D image, with such distant galaxies, the baseline between the two images would need to be 5 million light years. Imagine having one eye here and the other twice the distance to the Andromeda Galaxy. The small background galaxies are probably of the order of 1 billion light years away and their parallax would be close to zero, so these become the background effectively at infinity. Then using trigonometry I calculated the parallax for the two galaxies at 140 million light years and the edge on spiral at 90 million light years. The x dimension for Gary's image was 3911 pixels equivalent to 790 arc secs. I calculated that the parallax displacement for the nearer galaxy NGC 5981 at 52 pixels and for the more distant NGC 5982 and NGC 5985 at 31 pixels. In Photoshop I then rotated the image 90 degrees as the portrait aspect makes the 3D thing easier and duplicated it. In the 2nd image I removed the galaxies and then displaced them by the requisite amount. I also erased the stars, which were superfluous. Indeed the parallax is so great they would not appear in the same FOV from one eye to the other. I then put the two images together side by side as you can see here. 

It works. I can see the galaxies floating in space with the edge on spiral NGC 5981 clearly closer than the other two and all against the background of the distant galaxies. I hope you can make it work too.