GT81 Focuser - they all like this ?

[Sp@ce_d]

Bit disappointed with the focuser on my recent addition to the fold so far. Just wondering if other owners have any had the same issues or if I've a bad 'un.

The focuser seems to be unable to take the weight of a CCD & FW without becoming way looser in comparison to my ZS71 which has practically the same focuser and went through an entire season without needing any attention with the same load.

It seems the small grub screws require tightening right up therefore leaving the rotator unusable and even then the tube still has flex in it.

The focus point is almost at the end of the drawtube travel so that doesn't help either.

Before re tighten

http://youtu.be/zqCFKq53sYg

After re tighten

http://youtu.be/eVtdFGP52ik

[Zakalwe]

Blimey! That looks appalling, and after being tightened it's not that much better!

It looks like it is not correctly tightened onto the body of the OTA?

I wouldn't be happy with that much slop in a focuser.

[wuthton]

If you've bought that new I think you'd be perfectly justified to return that.

William Optics produce some great telescopes but then ruin them with useless focusers.

[Stargazer33]

That looks terrible! I wouldn't be happy with that at all. Call the supplier and have a word to see what they are prepared to do for you.

[ronin]

As the scope is "gold" I think that would mean the focuser is an R&P type.

The earlier "red" ones used a Crayford.

This may be a bit of a generalisation but I think that was one of the changes that occurred between the Red and Gold variants.

If it is R&P then that is pretty bad.

You are not having a happy/easy time with that scope are you ?

[Demon Barber]

Hi just take your time in re tightening all grub screw equally very small movements and the tube adjusters take the same careful(small) adjustment,it seems this scope passed through the net at both production and dealer quality control,good luck,

Regards 

Mike

[Sp@ce_d]

Thanks..Yeah.. I'm going to have a tweak about with it. I was surprised how loose it had become so quickly! I don't mind having to adjust it if it sorts it out, I was just wondering whether it's common on these. My ZS66 & ZS71 are smooth & hold CCD & FW well. ZS71 (red) is almost the same focuser R&P & is a pleasure.

I set this up in a dual shooter config to do a shootout with my Esprit 80. The focuser on that was the opposite, stiff at first but is solid & dependable compared to this one. Rather disappointed as I thought WO's QC had one over SW's. The optics are spotless on this compared to my experience of SW scopes.

Anyway, I'm not worried if I can't sort it as my supplier is our sponsor so I know I'm in good hands if I can't. Guess I'd better let them know just in case tho.

Sent from my iPhone using Tapatalk

[Alien 13]

The issue you have does sound odd like you my ZS71 can hold focus all night even with almost 2kg hanging off it and is so smooth fingers crossed you get it sorted.

Alan

[Davey-T]

No don't think that's normal, I have a WO 110 FLT and the focuser is solid as a rock with all sorts of crxp hanging on it.

Dave

[FLO]

 I'm not worried if I can't sort it as my supplier is our sponsor   so I know I'm in good hands if I can't. Guess I'd better let them know just in case tho.

We are never far away 

The first video appears to show the focuser with it's three rotation grub screws and the chrome lock screw all loose. If that is the case then movement like that is not unusual and can easily be adjusted out. Gently tightening the three grub-screws until they are just about to bite will make a world of difference but you still need to tighten the chrome lock screw. 

The second video suggests the focuser draw tube also needs tensioning and it too has a chrome lock screw that must be applied when you have found the focus point. 

Hi just take your time in re tightening all grub screw equally very small movements and the tube adjusters take the same careful(small) adjustment

Demon Barber is right, make small incremental adjustments until you find the optimum point. Keep in mind you will need to retighten the same screws periodically, particularly if it is carrying a reducer, filter-wheel and camera. 

The focus point is almost at the end of the drawtube travel so that doesn't help either.

You are right and using a focus extender will enable you to achieve focus without needing to rack the drawtube out so far. 

I don't mind having to adjust it if it sorts it out, I was just wondering whether it's common on these. My ZS66 & ZS71 are smooth & hold CCD & FW well. ZS71 (red) is almost the same focuser R&P & is a pleasure.

We'll happy adjust it for you, if that helps    But you would still need to fine-tune it when setup at home ready for use and periodically readjust it as it loosens.

The mechanism used by WO for their R&P focusers is the same used by most other focuser manufacturers so if you have adjusted one you can adjust them all. Personally, I'd like them to use a harder material for the three rotation grub-screws but, to be fair, the design is effective (and a considerable improvement over some earlier WO focusers) and difficult to improve on without upgrading to the likes of Moonlite and Starlight Instruments. 

HTH, 

Steve 

[Sp@ce_d]

We are never far away 

The first video appears to show the focuser with it's three rotation grub screws and the chrome lock screw all loose. If that is the case then movement like that is not unusual and can easily be adjusted out. Gently tightening the three grub-screws until they are just about to bite will make a world of difference but you still need to tighten the chrome lock screw. 

The second video suggests the focuser draw tube also needs tensioning and it too has a chrome lock screw that must be applied when you have found the focus point. 

Demon Barber is right, make small incremental adjustments until you find the optimum point. Keep in mind you will need to retighten the same screws periodically, particularly if it is carrying a reducer, filter-wheel and camera. 

You are right and using a focus extender will enable you to achieve focus without needing to rack the drawtube out so far. 

We'll happy adjust it for you, if that helps    But you would still need to fine-tune it when setup at home ready for use and periodically readjust it as it loosens.

The mechanism used by WO for their R&P focusers is the same used by most other focuser manufacturers so if you have adjusted one you can adjust them all. Personally, I'd like them to use a harder material for the three rotation grub-screws but, to be fair, the design is effective (and a considerable improvement over some earlier WO focusers) and difficult to improve on without upgrading to the likes of Moonlite and Starlight Instruments. 

HTH, 

Steve 

Evenin' FLO.... you beat me to it..  It's like having the Fairy God Mother Father watching over us..

Yup the grub screws came loose but the lock screw was tight. They didn't appear loose when I got it. When it arrived last week I gave it a thorough check over & was well impressed with the packing & cleanliness. The thing that shocked me (Not sure I really want to test my cushioned flooring in the Obsy) was how loose it had become after only slewing around a few stars to run some FocusMax V curves & a few short test subs. I couldn't understand why I was getting erratic results. The grub screws seem to need tightening right in fairly hard (don't want to force them) otherwise there's a gap appearing at the collar where it sags. This disables the rotation, as loosening the lock screw allows sag even though it wont rotate. Something that works fine on my ZS71.

The draw tube I need to take another look at. The lock isn't in use as I've fitted a stepper motor ( taken from my ZS71.. same fitting ). I wasn't expecting the focus point to be so far back & I reckon that's probably what's loosening the grub screws so quickly. I'm still waiting for the reducers to come in so I'm just using a flattener for now.  On my ZS71 it's the opposite, the tubes almost in.

Does the reducer make any difference to the amount of back focus on these?

Which focus extender is recommended? I prefer everything possible to be a screw thread to avoid flex.

I'm happy to adjust away, I'm going to take it off the mount and go over it all again as Demon Barber suggests. I have no problem with that. The only worry I have is how stable it will be, as most of the time I (attempt to) do my imaging remotely. So I won't be "on hand" to catch anything..

[Sp@ce_d]

Ok I feel much happier now I've stripped it down & I think I know what's happened.

The grub screws must have been just nipped up but still loose on the rotator & the lock screw was the only thing holding it tight. Although it felt tight enough to me when I put it all together as soon as it started slewing about the rotator worked loose. This is evident by the marking from the lock screw on the collar.

Now the tube is almost at the end of its travel when in focus & the 2 grub screws that hold that tight weren't even touching it. So its going to wobble about making the rotator looser even quicker.

I've adjusted it all and put it back together and now it feels like I expected.  I'll keep an eye on it. Hopefully it won't work loose again. Been trying to get first light with it under a full moon but now me guidings playing up.. & Maxim 6 has locked up again..arghh been one thing after the other lately.

so here's the 2 tube grub adjusters as they were

the mark where the rotator has slipped.. shame the lock screw isn't nylon tipped

the focus point outside

the focus point seen from inside.. notice how close to the end of travel.. this would have gone past during the FocusMax V curves routines so I definitely need to get an extension tube sorted.

Grub screws before

and screws moved into position ready for adjustment on re assembly