Arduino Barn Door Mount construction
Here are some suggested links to start with:
Daniel Berrangé – good article and discussion, with full instructions and links to free code etc.
You can buy various high quality genuine Arduino boards (called Genuino outside the US) made by the original Arduino people in Italy. My reading suggests a good one to choose for this application would be the Arduino Uno Rev3 £14.40
You can buy pin and code compatible Arduino clones from lots of other manufacturers, since the hardware design is open source. You can get cheaper ones, smaller ones, battery driven ones, wearable ones, low voltage ones, etc. etc. etc.. Each has advantages and disadvantages. Once familiar with Arduino, it would probably be possible to make an informed choice and get one of these instead of a genuine Arduino. A list of the myriad of clones, with pictures, is here:
EasyDriver stepper motor driver board £9
Nema-17 Bipolar Gearless Stepper Motor £17.50
Nema-17 Stepper Motor wiki
AccelStepper code library
Allows acceleration code during drive. Although if you go Type 4 design, you could use the standard Arduino stepper motor constant drive – easier!
Exoplanet transit targets
David Schneider – DIY Exoplanet Detector
Dave Trott – Double Arm Barn Door Mount
Arduino controlled Double Arm Barn Door Mount pictures
Some examples of barn door tracking photos