I don't profess to having a great knowledge of Photoshop, quite to the contrary. I utilize Photoshop for sizing my images and that is about my limit, but I found this really cool planet tutorial and had to give it a try. I've written out my steps for you just under my photos.
This is the photo I began with, taken by myself on my visit to Chicago in 2005.
And this is what I have done with it in Photoshop -
• Select a panorama or landscape photo.
• Select image size, have 'Constrain Properties' off and make the height and width the same value so as to make your image square.
• Select Filter - Distort - Polar Coordinates in the menu bar.
• Select Rectangular to Polar
• Select Image - Rotate Canvas - 180º
There are more steps in the actual tutorial for cleaning up the join, etc. but I haven't had the time to play around with those steps as yet.
I hope you have fun with this!