David, there are plenty of links for those with thinner pockets, but who have the wish and ability to DIY.
Try those:
http://soundstepper.sourceforge.net/ ( I am using this system, low cost and very accurate, requires PC or lap running windows)
http://www.bbastrodesigns.com/StepperSystem.html (I am still using this sytem on my dobson, requires cheap PC or lap running DOS)
Lowe cost alternative to Argo Navis could be this:
http://eksfiles.net/digital-setting-circles/
https://www.google.com.au/search?client=firefox-a&hs=bw1&rls=org.mozilla:en-GB
fficial&channel=sb&biw=1775&bih =752&tbm=isch&source=univ&sa=X&ei=D FxyVObALs3k8AWLwoGoCw&ved=0CBwQsAQ& q=encoders%20telescope%20images
http://www.iceinspace.com.au/forum/s...light=encoders
There was a lot od disussion about this subject on this forum in the past.. see some links below (just tri search for "Bartels" or "Stepper motors".. or "GoTo dobson" or "encoders"..)
http://www.iceinspace.com.au/forum/s...ht=Mel+bartels
http://www.iceinspace.com.au/forum/s...ht=Mel+bartels
http://www.iceinspace.com.au/forum/s...ht=Mel+bartels
Also, there were some Arduino projects on web..
And of course, PicGoTo. Great project.... It doesn't require PC or laptop as it has it's own processor:
https://sites.google.com/site/picgoto/english-manual
https://www.google.com.au/search?q=P...w=1775&bih=752