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Equipment Discussions >> Refractors

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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
William Optics GT81 Triplet Arrives
      #4842027 - 10/03/11 06:40 PM

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



P


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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4842030 - 10/03/11 06:43 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.



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.

P


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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4842081 - 10/03/11 07:02 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.

P


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zjc26138
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Reged: 02/24/05

Loc: Mingo Junction, Ohio
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4842131 - 10/03/11 07:30 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.


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Gary BEAL
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Reged: 05/10/03

Loc: New Zealand
Re: William Optics GT81 Triplet Arrives new [Re: zjc26138]
      #4842213 - 10/03/11 08:11 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


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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: Gary BEAL]
      #4842219 - 10/03/11 08:16 PM

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

P


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Gary BEAL
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Reged: 05/10/03

Loc: New Zealand
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4842581 - 10/03/11 11:48 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


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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: Gary BEAL]
      #4842594 - 10/03/11 11:56 PM

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



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

P


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Gary BEAL
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Reged: 05/10/03

Loc: New Zealand
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4842756 - 10/04/11 02:28 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


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George Ionas
member


Reged: 12/20/10

Re: William Optics GT81 Triplet Arrives new [Re: Gary BEAL]
      #4842821 - 10/04/11 05:15 AM Attachment (124 downloads)

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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George Ionas
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Reged: 12/20/10

Re: William Optics GT81 Triplet Arrives new [Re: George Ionas]
      #4842824 - 10/04/11 05:17 AM Attachment (153 downloads)

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

George


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Scott BeithAdministrator
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Reged: 11/26/03

Loc: Frederick, MD
Re: William Optics GT81 Triplet Arrives new [Re: George Ionas]
      #4842947 - 10/04/11 07:34 AM

Great setups and those are really pretty scopes!

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mandaragit
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Reged: 10/12/06

Re: William Optics GT81 Triplet Arrives new [Re: Scott Beith]
      #4843065 - 10/04/11 08:55 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...

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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: Gary BEAL]
      #4843149 - 10/04/11 09:43 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.

P


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SteveG
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Reged: 09/27/06

Loc: Seattle, WA
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4843475 - 10/04/11 12:48 PM

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.


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Gary BEAL
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Reged: 05/10/03

Loc: New Zealand
Re: William Optics GT81 Triplet Arrives new [Re: SteveG]
      #4843696 - 10/04/11 02:53 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


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George Ionas
member


Reged: 12/20/10

Re: William Optics GT81 Triplet Arrives new [Re: SteveG]
      #4843863 - 10/04/11 04:42 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.


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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: George Ionas]
      #4843877 - 10/04/11 04:53 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.

P


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Stargoat
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Reged: 04/10/05

Loc: Illinois
Re: William Optics GT81 Triplet Arrives new [Re: SteveG]
      #4844278 - 10/04/11 09:54 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


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Gary BEAL
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Reged: 05/10/03

Loc: New Zealand
Re: William Optics GT81 Triplet Arrives new [Re: Stargoat]
      #4844357 - 10/04/11 10:48 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


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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: Gary BEAL]
      #4844375 - 10/04/11 11:07 PM

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

P


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Pierre Stromberg
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Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: Stargoat]
      #4844381 - 10/04/11 11:12 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.

P


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Stargoat
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Reged: 04/10/05

Loc: Illinois
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4844471 - 10/05/11 12:54 AM

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


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3 i Guy
super member


Reged: 09/23/05

Loc: Tampa, FL
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4848848 - 10/07/11 12:07 PM Attachment (121 downloads)

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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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: mandaragit]
      #4856353 - 10/11/11 07:10 PM

There's only one left!

P


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Curmudgeon
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Reged: 09/04/11

Loc: Second star to the right, and ...
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #4856360 - 10/11/11 07:15 PM

Yow! What a beautiful scope! You must be very proud!

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George Ionas
member


Reged: 12/20/10

Re: William Optics GT81 Triplet Arrives new [Re: Curmudgeon]
      #4857043 - 10/12/11 05:08 AM

Well, I'm thrilled with my GT-81 (build number 6), it works very well with the AT2FF and also with the TRF-2008 0.8x focal reducer. Its build quality is similar to my FLT-132.

George


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wiro-sableng
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Reged: 11/03/11

Re: William Optics GT81 Triplet Arrives new [Re: George Ionas]
      #5010543 - 01/10/12 11:52 AM Attachment (66 downloads)

So, Now I'm the owner of GT-81 #15.
It's rainy season and cloudy sky almost every day here. But I trying it several time on this few weeks, and quite happy with it.

After a while, the focuser seems like didn't respond. If I tightened the focus lock, the focuser didn't move. If I loosened it, the focuser move by it self.

Does this is the focuser problem you guys talk about and need some tweaking/workaround, should I have to tightened some screw someplace?


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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: wiro-sableng]
      #5010572 - 01/10/12 12:13 PM

Hi Wiro. When I had an AT66 before the GT81, I experienced the same issue. I wound up increasing the tension on the focuser and all was good. There's probably a way to do this with WO OTAs too but I'm not familiar with how to do it.

I've had no problems with my own focuser and there's little play when rotating it. I'm very impressed with the usefulness of the DDG focuser. It's cloudy here in Washington State but in a test shot I was able to snap to focus immediately after establishing a reference value.

P


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wiro-sableng
member


Reged: 11/03/11

Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #5010593 - 01/10/12 12:29 PM

Quote:

Hi Wiro. When I had an AT66 before the GT81, I experienced the same issue. I wound up increasing the tension on the focuser and all was good. There's probably a way to do this with WO OTAs too but I'm not familiar with how to do it.

I've had no problems with my own focuser and there's little play when rotating it. I'm very impressed with the usefulness of the DDG focuser. It's cloudy here in Washington State but in a test shot I was able to snap to focus immediately after establishing a reference value.

P



Hi Pierre.
I'm glad to hear you have no problem with yours.
If anyone have similar problem with this OTA, I'd love to hear how they solved it. For now, focusing this OTA is really PITA for me.I hope it didn't involve buying new focuser.

If i can't fix this, I'll give this back to the dealer. It's still on warranty, so I don't want to do something which can avoid the warranty. Too bad, send it to repair mean it have to go shipping and could spend months.


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Jaap
member


Reged: 01/02/08

Loc: Netherlands, Almere.
Re: William Optics GT81 Triplet Arrives new [Re: wiro-sableng]
      #5010702 - 01/10/12 01:30 PM

Hi Wiro,

You can adjust the tension by tightening the black hex screw. That's the one almost in the middle of the black bottom plate, close to the big focus lock knob.
Usually it needs just a little bit of adjustment

Jaap.


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wiro-sableng
member


Reged: 11/03/11

Re: William Optics GT81 Triplet Arrives new [Re: Jaap]
      #5010722 - 01/10/12 01:40 PM Attachment (72 downloads)

Quote:

Hi Wiro,

You can adjust the tension by tightening the black hex screw. That's the one almost in the middle of the black bottom plate, close to the big focus lock knob.
Usually it needs just a little bit of adjustment

Jaap.




Hi Jaap, thanks.
Do you mean this screw?

[edit]
It's that screw.
A Simple adjustment that save my day... er night
Thanks Jaap.

It will be great if WO supplied this OTA with manual book so user didn't have to take a guess.
[/edit]

Edited by wiro-sableng (01/10/12 03:08 PM)


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Jaap
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Reged: 01/02/08

Loc: Netherlands, Almere.
Re: William Optics GT81 Triplet Arrives new [Re: wiro-sableng]
      #5010864 - 01/10/12 03:08 PM

Yes, that's the one.

Jaap.


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wiro-sableng
member


Reged: 11/03/11

Re: William Optics GT81 Triplet Arrives new [Re: Jaap]
      #5010870 - 01/10/12 03:10 PM

LOL. I post my edit at the same time you confirmed it.
Thanks again..


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Goodchild
scholastic sledgehammer
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Reged: 12/31/08

Re: William Optics GT81 Triplet Arrives new [Re: wiro-sableng]
      #5011106 - 01/10/12 06:14 PM

My question would be why isn't this adjustment tested before shipment? Does the "QC" sticker mean anything?

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Jared
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Reged: 10/11/05

Loc: Piedmont, California, U.S.
Re: William Optics GT81 Triplet Arrives new [Re: Goodchild]
      #5011167 - 01/10/12 07:10 PM

Even if it is tested before shipment, as parts start to "wear in" it will need periodic adjustment. Wiro-sableng mentioned that it was fine when he got it but loosened up with use. Not unusual for a focuser (even the best of them).

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Stargoat
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Reged: 04/10/05

Loc: Illinois
Re: William Optics GT81 Triplet Arrives new [Re: Goodchild]
      #5011174 - 01/10/12 07:15 PM

I'm also less than satisfied with the lack of "QC" control of this focuser. Scopes #15 thru #84 have all shared issues with the focuser. Indeed an owner’s manual would have been nice. On line at WO they show how to adjust and or tear down the focuser. But beyond the simple adjustments, I do not feel comfortable trying to make other adjustments...and really should not have to IMHO. I also had to adjust the play when rotating the focuser with the 3 equally spaced hex screws closest to the body of the scope. It was a balancing act while loaded up with heavy eyepieces or camera gear. There is no mention of this on the instructions, but thru the information on this group, I was able to make the adjustments.

The scope was packed well enough that these hex screws should not have all came loose from vibration during its transit from WO.

The new Zenithstar70 now has a rack and pinion focuser. I believe it is too small to be able to retrofit to the GT81.

So the question begs, has anyone retrofitted their GT81 with a Feathertouch focuser, and if so what model and adapters are required to do so?

Stephen


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Pierre Stromberg
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Reged: 02/07/08

Loc: Woodinville, WA
Re: William Optics GT81 Triplet Arrives new [Re: Stargoat]
      #5011536 - 01/10/12 11:34 PM

Just a note, #84 (my scope) did not show an issue with the focuser after all. My play was normal when loosened. It was tight when the screws were in place.

P


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Gary BEAL
Pooh-Bah
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Reged: 05/10/03

Loc: New Zealand
Re: William Optics GT81 Triplet Arrives new [Re: Pierre Stromberg]
      #5012256 - 01/11/12 01:26 PM

Stargoat,
mine sports, when I am imaging anyway, a F/T. I had an adaptor to fit a similar refractor rear cell, and accept the FT, and it was a simple matter of lathing out the adaptor so it fitted the rear of the GT-81. In my case this adaptor is about 80mm long, but I still use a "riser" an extension tube if you like, to get focus, as there is heaps of back-focus with the GT-81.
The addition of the F/T, and the motor makes the GT-81 sing.
Trouble is, I found a nice Lomo 80/840, and need to sort out which scope goes and which stays, difficult.
Gary


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Jaap
member


Reged: 01/02/08

Loc: Netherlands, Almere.
Re: William Optics GT81 Triplet Arrives new [Re: Gary BEAL]
      #5012307 - 01/11/12 02:00 PM

Hi Stephen,

I have ordered the new lightweight FT (FT2020BRC-LW) with adapter (A20-271) and 2 risers (2.75" and 3.75").
It should be here next week.

Jaap.


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