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William Optics GT81 Triplet Arrives

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#1 Pierre Stromberg

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Posted 03 October 2011 - 05:40 PM

So it arrived. Number 84 of a limited edition run of apparently 99 units.

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#2 Pierre Stromberg

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Posted 03 October 2011 - 05:43 PM

Check out the view underneath. Wacky. I read that there's a screw for photo tripods underneath but it's not readily apparently to me where it is. The red ring underneath is already fitted with an allen screw.

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I had planned to use one of my extra dovetail bars to start using it but I'm not sure that's in the cards after all. I guess I may really be forced to use rings but I really wish I didn't have to do that.

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#3 Pierre Stromberg

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Posted 03 October 2011 - 06:02 PM

Yup, the little black screw in the underside of the red ring comes out so you can attach it to a photo tripod. In my case though the tripod has a lever that collides with the focus tension knob.

Strange also that the camera tripod hole is below the recess for the dew cap. So it's impossible to attach a long dovetail to the OTA. Why did they do this and why didn't they at least include an L-bracket? Does anybody sell L-brackets until I get scope rings? Thanks for any info.

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#4 zjc26138

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Posted 03 October 2011 - 06:30 PM

Beautiful scope!

I'm not sure where you can find a an L-bracket at, but if you're sorta handy with tools I think you could make a L-bracket out of some wood and a couple of bolts. Just an idea.

#5 Gary BEAL

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Posted 03 October 2011 - 07:11 PM

I've had the same scope for ages, and like it. It sure is nuggety, and not light at all.
I agree, the thought that went into it wasn't from a users point of view, more it was designed I reckon in a 3D computer program, but someone that hadn't actually used the scope.
Glaringly obvious is the fact that the tripod head attaching to the 1/4x20 hole is not going to work. So you buy tube rings (I did, bought the W/O tube rings), and it sort of works.
But again, that 3D program didn't think about the dovetail, or the point of balance, so when you factor all that in and then think you'll rotate that focuser, you can't. See what I mean?
Sound likes I dislike it? No way, it is a great scope, but you have to be prepared to live with the R&D short-comings, and there are a few of them.
My only other beef is the DDG, in my case it either slips, or is that tight it hardly moves. When I image I use a Feather Touch, so get around this, but it will be the end of the scope sooner or later. At least I don't suffer image shift with the F/T like I do with the DDG.
Gary

#6 Pierre Stromberg

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Posted 03 October 2011 - 07:16 PM

Interesting. So when you put on the scope rings, did you have to remove the handle?

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#7 Gary BEAL

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Posted 03 October 2011 - 10:48 PM

No, the W/O rings fit and the handle is darn handy. I did have to rotate the scope a tad when I put a guide scope rail on the top of the rings, but this was to allow the handle to clear the guide-scope, and was not hardship to have it slightly rotated.
The handle is a great idea.
Gary

#8 Pierre Stromberg

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Posted 03 October 2011 - 10:56 PM

I think I may have found a great solution with the Lunt 4 inch dovetail.

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The dovetail is also slightly curved so it hugs the curvature of the tube quite nicely. Quite solid.

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#9 Gary BEAL

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Posted 04 October 2011 - 01:28 AM

Good one. Now, with the tube (and all it's bits and pieces attached) at it's balance point in the saddle, can you rotate the focuser. I can't, but admittedly, I have a Losmandy D series rail attached, via the tube rings. Try it and let us know.
Gary

#10 George Ionas

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Posted 04 October 2011 - 04:15 AM

I purchased a set of tube rings from WO with the scope and fitted the Losmandy D series doveplates to the top and bottom of the tube rings. I have no problem in rotating the focuser.

The balance point is located close to the middle of the saddle plate but this will depend on the weight of the camera/filterwheel gear attached to the focuser.

George

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#11 George Ionas

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Posted 04 October 2011 - 04:17 AM

Here is a closer view of the underside showing the doveplate/focuser clearance.

George

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#12 Scott Beith

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Posted 04 October 2011 - 06:34 AM

Great setups and those are really pretty scopes! :bow:

#13 mandaragit

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Posted 04 October 2011 - 07:55 AM

That's a very pretty scope! Do let us know what's it like under dark skies, I haven't seen alot of reviews for this scope...

#14 Pierre Stromberg

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Posted 04 October 2011 - 08:43 AM

Gary, I'm able to rotate the focuser quite nicely. The focus rotater lock does collide with the dovetail but that's pretty superfluous considering there's a stop on the focus rotater at that orientation anyway.

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#15 SteveG

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Posted 04 October 2011 - 11:48 AM

It's been pretty cloudy here in Woodinville - now I know why!

Congrat's on the new scope Pierre - hope it works out.
If you have play in the focuser rotating mechanism, you can adjust it out with the 3 black recessed allen screws that are closest to the tube. I had to tweak mine, but once I got it right there's been no further adjustment needed.

#16 Gary BEAL

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Posted 04 October 2011 - 01:53 PM

Well in my case I cannot rotate the focuser not significantly anyway. The scope with camera equipment on the end balances at about the red rear section, about the rear end of the short plate George shows in his photo. So, this is where the centre of the saddle needs to be. I use a longer gal, so I can balance the scope properly, and this will not allow rotation of the focuser at all. Without too much after-market engineering, all I can see that will allow this is a set of suitable riser blocks, to "lift" the scope up from the rail, and give enough room to clear the rail. Practical? I don't think so. Easier to just rotate the camera by loosening the set-screw on the draw-tube end.
Gary

#17 George Ionas

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Posted 04 October 2011 - 03:42 PM

Steve, I too had to tighten the 3 black recessed allen screws to remove the slightest amount of play in the focuser rotating mechanism, but once done no further adjustments have been required.

As an imaging scope the GT-81 fitted with the Astro-Tech AT2FF field flattener or using the Tele Vue TRF-2008 0.8x Photo Reducer Flattener produces excellent star images across the APS size CCD chip.

#18 Pierre Stromberg

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Posted 04 October 2011 - 03:53 PM

Interesting. My focuser doesn't seem to have any play at all. I wonder if WO got this feedback and added this inspection step before shipping.

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#19 Stargoat

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Posted 04 October 2011 - 08:54 PM

Glad to finally see aome other folks who picked up the GT81. I have #047. This is my first WO scope and a owners manual would have been nice to show these simple adjustments. My focuser when rotated also had a lot of play. It would go back into position when I'd tighten down the locking knob. I just adjusted the three black slotted head set screws to eliminate the play. Thank you for the adjustment tip.

Last night imaging the moon with my Canon 5D for the first time all went well with the focuser until the end of my session. When I went to rack the focuser back in with camera/extention tube still attached the focuser would not rack in. Something has loosened up causing the focuser to slip. I have been viewing with a TV 31 Nagler w/o problems which with the diagonal is heavier than the camera.

So what adjustments do I need to make. WO has published a detailed instruction manual for the 3" DDG on their website. It looks like item "B" hex screw (M5) is the first place to start with to adjust.

Has anyone else had their focuser not be able to rack in with a load when the scope is not horizontal? If so, what adjustments did you make?

Stephen

#20 Gary BEAL

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Posted 04 October 2011 - 09:48 PM

Me. Not many adjustments exist. It is basically tension on the one hex screw and that's it. If tight the focuser is stiff. If loose, well you know what happens, it already is. For all it is touted to be, the DDG is not really any better than the previous focusers. My $0.02c worth anyway. Mine now images with a Feather Touch, motorized makes a heap of difference.
Gary

#21 Pierre Stromberg

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Posted 04 October 2011 - 10:07 PM

Reexamining my GT81 tonight, it indeed has play too on the focuser. Thanks for everybody's advice on tightening it up.

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#22 Pierre Stromberg

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Posted 04 October 2011 - 10:12 PM

Hey Stargoat, regarding your problem about the focuser not being able to rack in, check your focus lock screw underneath your focuser. It'll let you focus out but not back in if you go all the way out while the focus screw is locked down. Try that first before you start adjusting the tension.

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#23 Stargoat

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Posted 04 October 2011 - 11:54 PM

Hello Pierre,

Thanks for the tip. Focus lock screw is in non tension state. I tightened the tension hex set screw without going too tight, and that has solved the problem. Upon close inspection I see that the single focus knob wobbles slightly as the focuser is rotated. The dual speed knob does not do this. So I need to see if another type of adjustment is required to the bearing block or something.

Stephen

#24 3 i Guy

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Posted 07 October 2011 - 11:07 AM

Say hello to #90. What a pocket-rocket this scope is. It's a big improvement over my 100ED for grab n go purpose. It shows a more crisp, asthetically pleasing star image than the doublet, at least to my eyes. Gary's right, she's a chunk but I LOVE her!! Nice job Pierre and George, I like both of your mounting solutions over mine, I kinda made do with what I had on hand. I finally found a use for the extra dovetail from my CG-5 and stacked 2 dovetails to get the clearance so my focuser could rotate.

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#25 Pierre Stromberg

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Posted 11 October 2011 - 06:10 PM

There's only one left!

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