Is this broken

[Sparkie67]

Hi, thanks for letting me join.

bought a telescope a few years ago.

I recently acquired a WO zenithstar II ED doublet 80mm

I’m trying to figure out if this is a 10:1 focuser, but the black knob just turns at the same speed as the larger 1.

Looked on the WO site for instructions, but not sure if they apply to this model.

I’d just like to be sure before I dismantle something that may not need it.

attached are a couple of pictures.

Many thanks

Andy

[Stuart1971]

Yes that is a 10:1 focus knob, and the black one should turn 10 times while the larger one just once…so looks like you have an issue, maybe it’s seized somehow…🤔

[Sparkie67]

Thanks for the info. I thought it might be, but wanted to make sure.

Looking at some videos and most focuser date clamped on the bottom of the housing.

This one passes through the body which could be interesting to get out.

I got the scope with a 1.25 and 2 diagonal with desiccant caps, standard tripod shoe and the WO clamp rings for £200, not sure if it was a bargain or not.

Edited March 7, 2022 by Sparkie67

[Stuart1971]

1 hour ago, Sparkie67 said:

Thanks for the info. I thought it might be, but wanted to make sure.

Looking at some videos and most focuser date clamped on the bottom of the housing.

This one passes through the body which could be interesting to get out.

I got the scope with a 1.25 and 2 diagonal with desiccant caps, standard tripod shoe and the WO clamp rings for £200, not sure if it was a bargain or not.

If you remove the fine focus knob, and then the focus knob on the other side the whole thing will slide out, or you can leave it in place as when you remove the fine focus you can then get to the workings of that without removing the whole thing….it should be quite easy, the fine focus runs on bearings by friction, you should see this and be able to see what the issue is….👍🏼

[Sparkie67]

Thanks, just ordered a set of Allan keys, typically the smallest that I need is missing from my set, and I can’t find it in the bottom of my tool bag either.

A screw to remove the black knob, another to remove the larger silver knob.

in the body there is 1 screw appears to be holding a collar, then a through hole which I can see a rotating brass collar with a screw in that. 
Looks easy enough to get apart though.

thanks

[Stuart1971]

3 minutes ago, Sparkie67 said:

Thanks, just ordered a set of Allan keys, typically the smallest that I need is missing from my set, and I can’t find it in the bottom of my tool bag either.

A screw to remove the black knob, another to remove the larger silver knob.

in the body there is 1 screw appears to be holding a collar, then a through hole which I can see a rotating brass collar with a screw in that. 
Looks easy enough to get apart though.

thanks

Correct, one grub screw in hole on each knob, and to remove the full dual focus section it’s the outermost screw in the hole on the black body…👍🏼

Edited March 7, 2022 by Stuart1971

[Ricochet]

Before you start taking things apart, try tightening up the grub screws. I had a fine focus not working on one of my focusers recently and the problem was that a grub screw was loose so the mechanism wasn't engaging. 

[Sparkie67]

Thank you will give that a go first. See what happens.

[Sparkie67]

Hi.

a quick update. Finally got an Allen key to fit, 1/16” hex key, nice snug fit.

the silver shaft is stuck in the brass housing.

after gentle warming and a small pin punch I have managed to knock it out.

the shaft has marks on it that stop it from rotating in the brass housing.

the marks look like it’s been in a squashed evenly on either side, in 3 places.

now if I filed them smooth with fine emery, what is to stop the shaft from then falling out of the housing.

or are they there to stop the shaft from moving, but maybe the scope was dropped on the knob, forcing the indent into the brass.

attached a picture but not sure if you can see the marks.

[Stuart1971]

1 hour ago, Sparkie67 said:

Hi.

a quick update. Finally got an Allen key to fit, 1/16” hex key, nice snug fit.

the silver shaft is stuck in the brass housing.

after gentle warming and a small pin punch I have managed to knock it out.

the shaft has marks on it that stop it from rotating in the brass housing.

the marks look like it’s been in a squashed evenly on either side, in 3 places.

now if I filed them smooth with fine emery, what is to stop the shaft from then falling out of the housing.

or are they there to stop the shaft from moving, but maybe the scope was dropped on the knob, forcing the indent into the brass.

attached a picture but not sure if you can see the marks.

Where are the ball bearings from the 10:1 reduction, were they missing….😮😮

[Sparkie67]

Hi, no it was all there. 3 large and about 10 small from the rear.

When the focuser is working correctly, as you turn the normal focus knob, should the fine adjustment knob spin on its own shaft quickly.

When I reassembled it the fine focus works, not smoothly, but the normal focuser is now jammed. The bearings in the housing won’t allow the fine focus knob to spin.

[Stuart1971]

1 hour ago, Sparkie67 said:

Hi, no it was all there. 3 large and about 10 small from the rear.

When the focuser is working correctly, as you turn the normal focus knob, should the fine adjustment knob spin on its own shaft quickly.

When I reassembled it the fine focus works, not smoothly, but the normal focuser is now jammed. The bearings in the housing won’t allow the fine focus knob to spin.

Yes, the fine focus knob will always spin 10 times to 1 turn of the full focus knob…

[Stuart1971]

You need to pack it with lithium grease too..👍🏼

[Sparkie67]

Cool, will look at that as well. I think this has been apart before and reassembled badly or with an incorrect shaft. 
will order some stainless rod and see how it goes.

 

thanks again.