Just like to share this small modification I've made to the GSO focuser that comes now on the RC10 and 12 scope (I think). The linear bearing in the focuser is actually quite good and I cannot feel any play or give in it. I found the biggest problem is the method GSO used to fix the inline (with the scope tube) location of the drive shaft. When the drive was tightened enough to move my focuser/camera (about 1kg), I could see the pressure screw rocking back and forth as I adjusted the focus. i.e. the drive shaft was moving and giving a mushy sloppy feeling to fine focus.
What I did was made two phospher bronze bushes to fit on the drive shaft that would precisely fit the grove cut into the focuser tube to take the shaft. So the drive shaft is now supported longitudinally in precise fitting bushes. Anyway pictures are worth a thousand words so see them attached. Fit is very important to reduce play to near zero. The result is a greatly improved feel with precise control over fine focus. Well worth an hour or so if you have a small lathe.
I'll have to look into this on mine. It seems to lose fucus when I tighten up the focus lock. Could be movement in the control allowing it to rock.
Got a lathe, got some brass.
I made something similiar for my GSO linear focuser in my 10" imaging newt. I used plastic tube that I had on hand, no idea where I got it orginially but it works fine.
After doing the previous two mods I was satisfied this focuser would perform well enough to make an auto focus unit for it. The unit uses a stepper motor to drive the focus shaft via a small toothed belt - zero backlash. An Arduino based controller does the controlling. ASCOM focus driver in C# controls the unit via usb serial port. Whole unit designed in AutoCAD Inventor and parts machined on home CNC mill and anodized at home. The electronics is just hooked up to allow experimenting with stepper driver and controller. Final step is to add temperature compensation. The whole unit works very well with FocusMax and MaximDL.
