Hi,
I am looking at purchasing an 80mm apo f6 to f7.5 for astrophotography - What focusser type is best for me a crayford or dual speed rack and pinion?
Crayford focusers are generally considered better mainly because they have no backlash, are more precise and usually smoother. They are usually more expensive. However you should try before you buy (or check some out at a club observing night) as there are good and bad in either. Hope this helps.
Crayford is a nice change from a standard made rack and pinion but a well made rack and pinion is a nicer change from a standard Crayford especially for heavy loads. Feathertouch R&P are more expensive than their Crayford offering and yet their Crayfords are some of the best available. Have a read of some of the user reviews on their web site for the R&P.