Astrophotography
A very useful website with a page on Astrophotography has been produced by Carole Pope who has been published a number of times.
https://sites.google.com/site/caroleastroimaging/home
Making Every Photon Count.
http://www.nightskyimages.co.uk For Steve Richards' website. I purchased my copy of his book from http://www.firstlightoptics.com
Barn Door Tracker
Gary Seronik's page describing his Barn Door Tracker.
http://www.garyseronik.com/?q=node/52
Rob Paisley's page describing a stepper motor controller is no longer available
Electronic components
Parts for the fan speed controller and and stepper motor controller on the barn-door tracker have been obtained from
Field battery
Batteries for the field battery were obtained from Tayna batteries Abergele.
https://www.tayna.co.uk/Mobility-Batteries-C28.html
Stellarmate Gadget
You have a choice over buying the gadget with Stellarmate already installed or installing the software yourself on a micro SD card for use with a Raspberry Pi. The website has full details.
https://www.stellarmate.com/products/stellarmate-os.html
Plate Solving
A useful site for platesolving is https://nova.astrometry.net/ which can return a result within 10 minutes.