May be you have seen home planetarium but the one showing galaxy like are rare ( I haven't seen one yet myself). So I decided to make this super easy-dirt cheap galaxy planetarium. Head on and you will be having your own in less than 5 minutes.
Step 1: Materials Required
You will need:
1 Plastic Glass
1 thin needle ( you can use anything which is pointed and has more thickness than the needle)
1 medium thickness nail
1 flashlight (mine was Blue LED based. I don't know whether ordinary bulb flashlight will work or not since for "Diffraction" and "Interference" to take place(on which my planetarium is based) you need a monochromatic light .Simply just use a LED flashlight.
Step 2: Assembly
All you have to do is just wrap the foil on the outer side of the glass( take care that the foil doesn't tear at any place). Do not wrap the foil in the interior(well you can but I didn't tried that, so do your own experimenting).
Now make holes by needle on the foil covered glass. Then make holes using the nail. You can refer to pictures.
Step 3: How to Use
Place the flashlight below the glass as shown on the picture. If the flashlight is larger than the cup's circumference then you have to cover the extra leaking light with electrician's tape. Now switch on the flashlight, switch off the room lights and project the image on a wall and enjoy your galactic ride.
Try with different pattern of holes and every time a new galaxy will be born.
How it works:
It works on diffraction mainly which is distortion due to very small slits and holes which is due to the wave nature of light. Also the rough and reflective edges of aluminium foil also helps in reflecting and distorting the light creating a galaxy like pattern.
Check out other exiting experiments on http://scimad.com/