Williams Optics 81GT

[AlistairW]

Hello,

Bit of a noob question. But on my refactor, you can turn the end of the assembly (near the focuser) by unscrewing a thumb screw. This is so you can orientate the eyepiece in a better position for observing. However I notice that even when the thumb screw is up tight, there is still a bit of wiggle between the main body of the scope and the part where the focuser is. Hope that makes sense ? - However is this wiggle (probably about 1mm) an issue ?  - I don't think it is, but wanted to check.

Thanks

Alistair

[red dwalf]

i would say that for visual use then no problem, for imaging use then certainly, you want no movement or slop in the focuser or assembly, if you look around the edge where the thumb screw is, you`ll see a couple of small allen key screws which can be tightened slightly just enough to eliminate slop movement, then when the thumb screw is tightened it should be solid.  

[ronin]

Unfortunately for a scope like the GT-81 the focuser was the weakest item on it (in a way).

It is I half guess not really worse then any other Crayford focuser, the design is reliant on friction and that is not exactly a great idea and so .

You can upgrade it but that route is costly - Feather Touch or Moonlite

I have a Megrez 90 and I will say that when I do up the thumbscrew (single one) the focuser does not move up or down at all, and it is not exactly wound in heavily. Just checked and I notice there is a screw head diagonally opposite the thumbscrew - not sure what this does but it might be that you can make a quarter or half turn in and then the thumbscrew tightens the focuser more fully. In effect there are 2 screws but only one is easily adjustable. ALL depends on the units being similar

[Davey-T]

Later GT81s should have a rack and pinion focuser.

Dave

[lensman57]

Hello,

Bit of a noob question. But on my refactor, you can turn the end of the assembly (near the focuser) by unscrewing a thumb screw. This is so you can orientate the eyepiece in a better position for observing. However I notice that even when the thumb screw is up tight, there is still a bit of wiggle between the main body of the scope and the part where the focuser is. Hope that makes sense ? - However is this wiggle (probably about 1mm) an issue ?  - I don't think it is, but wanted to check.

Thanks

Alistair

I don't have a GT81 but I do have 3 other WO scopes. There are normally 3 little nylon grub screws around the rotating part of the tube that need to be gently tightened until you are just able to rotate the focuser assembly. Once done then the large thumb screw can be gently tightened to lock the focuser in position. Hope this helps.

A.G

[AlistairW]

Lensman57 - Brilliant advise, I tightened those grub screw just a bit so that I could just rotate the assemble freely, but now when it locks, it is solid .... sometimes I wish there we instructions ! :-)

The are two other grub screws slightly set back from the three I have just tightened (towards eyepiece) ..... they seem to simply spin round, - any idea what they are for ? - (Didn't want to screw them too far in , in case they fell in to the OTA).

Thanks - Alistair

[lensman57]

Lensman57 - Brilliant advise, I tightened those grub screw just a bit so that I could just rotate the assemble freely, but now when it locks, it is solid .... sometimes I wish there we instructions ! :-)

The are two other grub screws slightly set back from the three I have just tightened (towards eyepiece) ..... they seem to simply spin round, - any idea what they are for ? - (Didn't want to screw them too far in , in case they fell in to the OTA).

Thanks - Alistair

Glad it worked. Not 100% sure about the two grub screws but looking at the photo of the GT81 they seem to be for mounting a finder shoe. As yours has top finder rings then these grubs are just redundant. I have used hem for the same purpose on all my WO scopes. Just unscrew them till the top of the screw is flush with the tube and leave them there as they are quite tiny and if lost dirt will get into the tube.

A.G