Not exactly astronomy, but it does relate to one of my telescopes...
Over the weekend I was taking some new photographs of my two 'scopes to replace those on the tools page of my site (the ones that had been there had been taken with mobile phones and were of terrible quality). While reviewing the shots yesterday I noticed that two of them appeared to be taken from almost exactly the same spot and at exactly the same height.
In other words, I appeared to have accidentally created a stereogram. I then placed them side by side in one image and got this result:
If you're the sort of person who can go cross-eyed without any trouble you should be able to see the 3D effect. Click on the image for a bigger version.