Focuser Slipping, please help.

[mrsnipey]

Hi there, I've had my new (well, second hand) 12" GSO dob for two days now and I must say that I haven't been so excited since I was a kid.

Everything is working well but I just noticed that when I'm looking at objects closer to the horizon the focuser doesn't seem to hold it's position and it slips all the way into the tube. It works fine when I stand the tube up though. I have played around with a few screws on the focuser but nothing I do seems to make it keep it's position.

I was using it a couple of hours ago and it was working fine and now that I've brought the scope back inside it seems to be "grabbing" a lot better when I tilt it down. Does this have something to do with the temperature of the focuser (the only thing I can think of at the moment) or maybe there was some moisture on the column on the focuser.

Can anyone please help me.

[mill (Martin)]

The screw closest to the tube should be turned out and the screw further away adjusts the tension.
Try that and it should be ok.

[mrsnipey]

Thanks for the quick reply.
I will try that and see how it goes.

That's what happens when you muck around with screws and you don't know what they're for.

I'll let you know how I go.

[mrsnipey]

Yep, that fixed it. Thanks heaps.
Feel like a fool, but a happy fool at that.

[Starkler (Geoff)]

These focusers don't come with any instructions so they catch many people out the first time.

The main gotcha is to keep the inner one totally loose otherwise you lose a large portion of the available outwards travel of the focuser. The challenge then is to avoid losing the screw. Maybe best to remove it totally and put it somewhere safe.