Now we need to drill a couple holes. The size of all the holes in this project except the last one are up to you, depending on what size fasteners you bought. The first hole needs to go in the base -we need to drill a hole near the center. The exact distance from the side is critical - it will need to run through the center of the lens. So, put your camera down on a table. Measure the height from the table to the center of the lens - that's the distance the hole in the base needs to be from the side.
If you're not using a swivel under the base, you'll need a fairly large hole here, as you'll need to install a socket (or 'insert nut') so the tripod can screw into the tripod head. The dimensions of that socket depend on your tripod - if you're planning to mount this to the screw that normally attaches to the camera, you want a '1/4-20' socket. Here's what an insert nut looks like:
The hole in the side is where the arm will pivot. As such, it needs to be in the same plane as the hole in the base. In other words, if you're looking at the unit from the side, the side hole will appear directly above the base hole. Make the hole in the side about 4 1/2 to 5 inches above the base - your camera will need room to swing downwards when you're shooting a picture of the sky.[Edited by Moderator on 12/19/2009 4:56:06 AM]