Using A Barn Door Tracker

Solidworks cad model of the barn door tracker.

Using a barn door tracker.

Polar alignment is the process of aligning the hinge of the tracker with the north or south celstial pole depending on your location. A barn door tracker also known as a haig or scotch mount is a device used to cancel out the diurnal motion of the earth for the observation or photography of astronomical objects it is a simple alternative to attaching a camera to a motorized equatorial mount. The next task is to bend the threaded rod to match the 11 43 radius so that the mount will track correctly as the barn door mount is rotated about it s hinge. You can get a lot of parts for a tracker from this guy google bencooper karoo barn door tracker.

In order to use the tracker it will need to be polar aligned. A sidereal day on earth is 23 hours 56 minutes and 4 091 seconds long or 1436 minutes about 4 minutes shorter than a standard solar day and we can use this time to calculate the rate at which the barn door tracker needs to turn. Using a piece of plywood large enough to layout a 11 43 radius using a compass scribe the radius onto the plywood. I have built a few trackers over the last few years using a slightly different design and a curved rod for greater tracking accuracy.

Just because of the limitations of the design and lengths of the bolts we can use a barn door tracker is only really capable of being used for approximately 8 10 minutes. This will counter the effects of the earth s rotation as you move the tracker. You need to turn the handle one full rotation per minute to compensate and match the earth s rotation and keep your stars aligned.