I think I posted this, might have made it into an email – it’s from a couple of years ago and the crux is – you have to have the perfect opposite images of the heavens – these are usually shown as Northern & Southern Hemisphere and regularly found on facing pages of an atlas like the Collins or Daily Telegraph editions.
These images are the subject and your objective is to overlap them by crossing your eyes without making your vision go blurred – more often than not there’s a useful concentric circle print on them so the centres can be lined up exactly and then what you will be seeing is a view of the space in the immediate part of the universe around us without planet earth obstructing your view…
Now I appreciate either image can be rotated (imagine two cogs working together) so that the view is slightly different and this is something I’ve yet to try* but for the time being – suffice it to say, if someone was stood in range of your peripheral vision tapping on a calculator and you asked them to stand aside a moment so you could focus this manual interlacing – you’d probably still see some kind of cosmic calculating going on as you overlapped the images by crossing your eyes without blurring…..
🙂 It’s fun, just don’t hurt yourself trying and blame me because I’ve just disclaimed any hurt with this statement :-p
*Now to make a slowly & smoothly rotating gif version 🙂