TheSkySearchers

Hi folks,

I just picked up a used 8" Classic Dob and the focus tube is wobbly, upon investigation I found the focus lock screw is missing, as is what I am guessing is a nylon or PTFE block that sits in a channel to protect the tube from the screw. The parts diagram in the user manual doesn't break down to this level of detail.

Anyone have a parts list for this? I'm sure it is common among most size reflectors and other brands which are from the same mfr in China.

I could also machine something if need be.

Cheers

If you could post a image of what you have it would help greatly.

Lady Fraktor wrote: ↑Thu Nov 16, 2023 4:04 am If you could post a image of what you have it would help greatly.

Basic scope



And my actual focuser

Well 2 of the images are the same
It seems you have the grub screws still but the tension screw and likely the plastic shim under it are missing.
The local hardware store should have a screw/ bolt and if the plastic slider that goes between the drawtube and tension screw is missing it can be made from any stiff plastic around 1/8" thick.
How do the teflon sliders inside the focuser look?
Rack & pinion in good shape?

When my focus lock screw got lost, I just replaced it with a simple nylon screw. It works great and is still in-place 2 years later.

Teflon slider looks fine but I haven't dismantled the focuser yet. Externally the rack looks good, I don't know if the inner tube is removable, it won't go out any further than the stop screw or whatever keeps it from falling out into the snow on the ground. :-) I'll dismantle it this weekend and fab something.

If there is nothing besides the lock screw and plastic block I'll just machine something in my shop Delrin, UHMW etc. I have an assortment of metric grub screws here.

Thanks for the help.

cheers

To conclude this topic....

I removed the mirror to clean it and found the plastic focus tube slider sitting beside the mirror in the housing, and I found a metric bolt in the shop that fits, M8x1.25. Lubed everything with Teflon grease and it works 100% again, nice and smooth. The mirror tuned out great as well, nice and shiny as well as the secondary. The M43 adaptor arrived today for the Lumix G7 but of course it's cloudy and snow is forecast, maybe later this week.

Cheers