[Mariner (Frank)]

Hi All,
I have searched the net but to no avail, I need some IIS expertise. My refrator is a cheap but cheerful Meade Starnavigator 102mm. I think it is about f7.7 or there abouts. I paid about $199US for it at costco last october. It has a nasty (but surprisingly stiff), very lightweight tripod. It has a really effective goto mount on it (the same meade 497 handset alone retails here for about the same price that I paid for everything - also had a 9mm & 26mm EP and software). I love it! THe eyepieces were pretty average and the diagonal was very flimsy. I replaced the diaginal with a better one from orion and I use my TV 32 and 15mm plossls instead of the EPs that came with it. I am very satisfied with it. Until I can afford a really nice refractor - this will do. This has been worth every penny as my 6yr old daughter struggles with the 12" dob but loves this little one - how many six yr olds can say they have seen the eye on jupiter or its moons or saturns rings - I wish I had at that age!
Having said all this (sorry about being long winded), I am very keen to get a good value crayford focuser for it as the rack style focuser with no fine adjustment that the scope came with as standard is the pits. I see that bintel sell several different sizes but, I have no idea which size would fit my scope? Does anyone know this scope or have any ideas what the inner diameter is or should be for fitting of a new focuser? Or how I even do it?

Any assistance would be very much appreciated.
Regards, Frank.