Barn door tracker
From Wikipedia, the free encyclopedia
A Barn Door Tracker, also known as a Haig or Scotch mount, is a simple device used to cancel out the diurnal motion of the Earth for observing, or for photography of, astronomical objects.
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[edit] History
The barn door tracker was created by George Haig. His plans were first published in Sky and Telescope magazine in April 1975.
[edit] Design
A simple single-arm barn door tracker can be made by attaching two pieces of wood together with a hinge. A camera is mounted on the top board, usually with some sort of ball joint to allow the camera to be pointed in any direction. The hinge is aligned with a celestial pole and the boards are then driven apart at a constant rate, usually by turning a threaded rod or bolt. This is called a tangent drive.[1]
This type of mount is good for approximately 5-10 minutes before tracking errors become evident when using a 50mm lens. That length of time can be increased to about 20 minutes when using an isosceles mount.[2]
These designs were improved upon by Dave Trott, whose designs were published in the February 1988 issue of Sky and Telescope. By using a second arm to drive the camera platform, tracking accuracy was greatly increased, and can lead to exposure times of up to one hour.[3]The most accurate of these designs is the Type-4.
The most basic of these designs are manually operated, although some have added electric motors to automate and improve the accuracy of the tracking process.
[edit] References
- Tonkin, Steve. A Better Barn door
- Gagnon, Steve. How to build a double-arm barn door tracker
- De Tray, Jeff. Build a Barn Door Tracker
[edit] See also
[edit] External Links
- A Better Barn door
- How to build a double-arm barn door tracker
- Build a Barn Door Tracker
- The Cosmic Canvas
![[1]](http://www.astunit.com/tonkinsastro/atm/projects/scotch1.gif){kind=link}
![[2]](http://www.astunit.com/tonkinsastro/atm/projects/scotch2.gif){kind=link}
![[3]](http://www.astunit.com/tonkinsastro/atm/projects/scotch3.gif){kind=link}