Great to see another OAG Newtonian user. This is mine
http://www.users.on.net/~josiah/focuser/IMG_9933.jpg
the OAG/Focuser unit was made by
http://www.aeroquest-machining.com/page9.html
Yes I get elongated stars, but the trick is to try and locate one where the elongation is at right angles to the RA direction. That way it is easier to detect drive errors as the elongated star moves off the reticle, and correct it. I have tried a modded webcam, but it isnt sensitive enough. One needs a monochrome webcam with a nice high Quantum effeciency. The DMK that Mike uses would be the go. I cant autoguide as my 20+ year old mount has no such provision, but have toyed with the idia of using a sensitive web camera to put the guidestar on a monitor running Guide Dog software that works on the "centroid" of the elongated guidestars, allowing me to just heep the indicator it puts on the star stationary.
Scott